Form data goes to `request.params`, `request.formData` is empty and crashing on iteration
I suppose that when data sent to server using POST, it shoud go to formData, not to params. Also crashing when trying to iterate is weird.

I use #head nim and jester 0.4.1

Code:
```nim
import jester, asyncdispatch

routes:
  post "/":
    echo request.params
    echo request.formData.len
    for name, value in request.formData.pairs:
      echo name
      echo value
```
Request:
```
$ curl -v -XPOST -d'test=boom' http://127.0.0.1:5000/
Note: Unnecessary use of -X or --request, POST is already inferred.
*   Trying 127.0.0.1...
* Connected to 127.0.0.1 (127.0.0.1) port 5000 (#0)
> POST / HTTP/1.1
> Host: 127.0.0.1:5000
> User-Agent: curl/7.47.0
> Accept: */*
> Content-Length: 9
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 9 out of 9 bytes
< HTTP/1.1 502 Bad Gateway
< Content-Length: 5649
< Server: HttpBeast
< Date: Sat, 08 Jun 2019 12:22:23 GMT
< Content-Type: text/html;charset=utf-8
<
(traceback goes here)
```
Compilation/run log:
```
Hint: used config file '/home/agent/.choosenim/toolchains/nim-#head/config/nim.cfg' [Conf]
Hint: used config file '/home/agent/.choosenim/toolchains/nim-#head/config/config.nims' [Conf]
Hint: system [Processing]
Hint: widestrs [Processing]
Hint: io [Processing]
Hint: test [Processing]
Hint: jester [Processing]
Hint: net [Processing]
Hint: nativesockets [Processing]
Hint: os [Processing]
Hint: strutils [Processing]
Hint: parseutils [Processing]
Hint: math [Processing]
Hint: bitops [Processing]
Hint: macros [Processing]
Hint: algorithm [Processing]
Hint: unicode [Processing]
Hint: pathnorm [Processing]
Hint: osseps [Processing]
Hint: posix [Processing]
Hint: times [Processing]
Hint: options [Processing]
Hint: typetraits [Processing]
Hint: sets [Processing]
Hint: hashes [Processing]
Hint: strtabs [Processing]
Hint: re [Processing]
Hint: pcre [Processing]
Hint: rtarrays [Processing]
Hint: tables [Processing]
Hint: uri [Processing]
Hint: mimetypes [Processing]
Hint: asyncnet [Processing]
Hint: asyncdispatch [Processing]
Hint: heapqueue [Processing]
Hint: lists [Processing]
Hint: asyncstreams [Processing]
Hint: asyncfutures [Processing]
Hint: deques [Processing]
Hint: cstrutils [Processing]
Hint: selectors [Processing]
Hint: epoll [Processing]
Hint: md5 [Processing]
Hint: logging [Processing]
Hint: httpcore [Processing]
Hint: asyncfile [Processing]
Hint: macrocache [Processing]
Hint: json [Processing]
Hint: lexbase [Processing]
Hint: streams [Processing]
Hint: parsejson [Processing]
Hint: strformat [Processing]
Hint: errorpages [Processing]
Hint: htmlgen [Processing]
Hint: utils [Processing]
Hint: cgi [Processing]
Hint: cookies [Processing]
Hint: request [Processing]
Hint: httpbeast [Processing]
Hint: future [Processing]
Hint: osproc [Processing]
Hint: cpuinfo [Processing]
Hint: linux [Processing]
Hint: parser [Processing]
Hint: patterns [Processing]
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(1273, 9) Hint: Asynchronous route: match. [User]
CC: stdlib_assertions.nim
CC: stdlib_dollars.nim
CC: stdlib_io.nim
CC: stdlib_system.nim
CC: stdlib_parseutils.nim
CC: stdlib_math.nim
CC: stdlib_strutils.nim
CC: stdlib_pathnorm.nim
CC: stdlib_options.nim
CC: stdlib_times.nim
CC: stdlib_os.nim
CC: stdlib_nativesockets.nim
CC: stdlib_hashes.nim
CC: stdlib_net.nim
CC: stdlib_strtabs.nim
CC: stdlib_tables.nim
CC: stdlib_uri.nim
CC: stdlib_mimetypes.nim
CC: stdlib_heapqueue.nim
CC: stdlib_deques.nim
CC: stdlib_cstrutils.nim
CC: stdlib_asyncfutures.nim
CC: stdlib_asyncstreams.nim
CC: stdlib_selectors.nim
CC: stdlib_asyncdispatch.nim
CC: stdlib_md5.nim
CC: stdlib_logging.nim
CC: stdlib_httpcore.nim
CC: stdlib_asyncfile.nim
CC: ../../../../../../home/agent/.nimble/pkgs/jester-0.4.1/jester/private/errorpages.nim
CC: stdlib_cgi.nim
CC: ../../../../../../home/agent/.nimble/pkgs/jester-0.4.1/jester/private/utils.nim
CC: stdlib_future.nim
CC: ../../../../../../home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast/parser.nim
CC: ../../../../../../home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim
CC: ../../../../../../home/agent/.nimble/pkgs/jester-0.4.1/jester/request.nim
CC: ../../../../../../home/agent/.nimble/pkgs/jester-0.4.1/jester.nim
CC: test.nim
Hint:  [Link]
Hint: operation successful (80370 lines compiled; 5.875 sec total; 112.074MiB peakmem; Debug Build) [SuccessX]
Hint: /mnt/c/Users/golds/Desktop/nbin/test  [Exec]
INFO Jester is making jokes at http://0.0.0.0:5000
Starting 1 threads
^CSIGINT: Interrupted by Ctrl-C.
Traceback (most recent call last)
/mnt/c/Users/golds/Desktop/nbin/test.nim(3) test
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482) serve
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423) run
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(286) eventLoop
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/ioselects/ioselectors_epoll.nim(383) selectInto
SIGINT: Interrupted by Ctrl-C.
Error: execution of an external program failed: '/mnt/c/Users/golds/Desktop/nbin/test '
[1] agent@DESKTOP-RGR7528 /mnt/c/Users/golds/Desktop/nbin [15:18] $ nim c -r test.nim
Hint: used config file '/home/agent/.choosenim/toolchains/nim-#head/config/nim.cfg' [Conf]
Hint: used config file '/home/agent/.choosenim/toolchains/nim-#head/config/config.nims' [Conf]
Hint: system [Processing]
Hint: widestrs [Processing]
Hint: io [Processing]
Hint: test [Processing]
Hint: jester [Processing]
Hint: net [Processing]
Hint: nativesockets [Processing]
Hint: os [Processing]
Hint: strutils [Processing]
Hint: parseutils [Processing]
Hint: math [Processing]
Hint: bitops [Processing]
Hint: macros [Processing]
Hint: algorithm [Processing]
Hint: unicode [Processing]
Hint: pathnorm [Processing]
Hint: osseps [Processing]
Hint: posix [Processing]
Hint: times [Processing]
Hint: options [Processing]
Hint: typetraits [Processing]
Hint: sets [Processing]
Hint: hashes [Processing]
Hint: strtabs [Processing]
Hint: re [Processing]
Hint: pcre [Processing]
Hint: rtarrays [Processing]
Hint: tables [Processing]
Hint: uri [Processing]
Hint: mimetypes [Processing]
Hint: asyncnet [Processing]
Hint: asyncdispatch [Processing]
Hint: heapqueue [Processing]
Hint: lists [Processing]
Hint: asyncstreams [Processing]
Hint: asyncfutures [Processing]
Hint: deques [Processing]
Hint: cstrutils [Processing]
Hint: selectors [Processing]
Hint: epoll [Processing]
Hint: md5 [Processing]
Hint: logging [Processing]
Hint: httpcore [Processing]
Hint: asyncfile [Processing]
Hint: macrocache [Processing]
Hint: json [Processing]
Hint: lexbase [Processing]
Hint: streams [Processing]
Hint: parsejson [Processing]
Hint: strformat [Processing]
Hint: errorpages [Processing]
Hint: htmlgen [Processing]
Hint: utils [Processing]
Hint: cgi [Processing]
Hint: cookies [Processing]
Hint: request [Processing]
Hint: httpbeast [Processing]
Hint: future [Processing]
Hint: osproc [Processing]
Hint: cpuinfo [Processing]
Hint: linux [Processing]
Hint: parser [Processing]
Hint: patterns [Processing]
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(1273, 9) Hint: Asynchronous route: match. [User]
Hint:  [Link]
Hint: operation successful (80370 lines compiled; 3.096 sec total; 112.078MiB peakmem; Debug Build) [SuccessX]
Hint: /mnt/c/Users/golds/Desktop/nbin/test  [Exec]
INFO Jester is making jokes at http://0.0.0.0:5000
Starting 1 threads
DEBUG POST /
{"test": "boom"}
0
ERROR /mnt/c/Users/golds/Desktop/nbin/test.nim(3) test
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482) serve
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423) run
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(287) eventLoop
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(219) processEvents
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(485) :anonymous
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(386) handleRequest
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311) dispatch
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(34) dispatch_continue
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(285) dispatchIter
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311) match
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(34) match_continue
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/collections/tables.nim(1258) matchIter
/home/agent/.choosenim/toolchains/nim-#head/lib/system/fatal.nim(39) sysFatal
[[reraised from:
/mnt/c/Users/golds/Desktop/nbin/test.nim(3) test
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482) serve
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423) run
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(287) eventLoop
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(219) processEvents
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(485) :anonymous
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(386) handleRequest
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311) dispatch
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(37) dispatch_continue
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(285) dispatchIter
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncfutures.nim(353) read
]]
[[reraised from:
/mnt/c/Users/golds/Desktop/nbin/test.nim(3) test
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482) serve
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423) run
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(287) eventLoop
/home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(219) processEvents
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(485) :anonymous
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(386) handleRequest
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311) handleRequestSlow
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(37) handleRequestSlow_continue
/home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(336) handleRequestSlowIter
/home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncfutures.nim(353) read
]]
index 0 not in 0 .. -1
Async traceback:
  /mnt/c/Users/golds/Desktop/nbin/test.nim(3)                                       test
  /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482)                             serve
  /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423)                       run
  /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(287)                       eventLoop
  /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(219)                       processEvents
  /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(485)                             :anonymous
  /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(386)                             handleRequest
  /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311)          dispatch
  /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(34)           dispatch_continue
  /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(285)                             dispatchIter
  /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311)          match
  /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(34)           match_continue
  /home/agent/.choosenim/toolchains/nim-#head/lib/pure/collections/tables.nim(1258) matchIter
  /home/agent/.choosenim/toolchains/nim-#head/lib/system/fatal.nim(39)              sysFatal
  #[
    /mnt/c/Users/golds/Desktop/nbin/test.nim(3)                                       test
    /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(482)                             serve
    /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(423)                       run
    /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(287)                       eventLoop
    /home/agent/.nimble/pkgs/httpbeast-0.2.2/httpbeast.nim(219)                       processEvents
    /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(485)                             :anonymous
    /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(386)                             handleRequest
    /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(311)          dispatch
    /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncmacro.nim(37)           dispatch_continue
    /home/agent/.nimble/pkgs/jester-0.4.1/jester.nim(285)                             dispatchIter
    /home/agent/.choosenim/toolchains/nim-#head/lib/pure/asyncfutures.nim(353)        read
  ]#
Exception message: index 0 not in 0 .. -1
Exception type:
```