Suspecting of memory leak in Jester with --gc:arc
I've tested a simple "Hello World" and compiled it with these parameters:
```
--define:release
--define:danger
--define:useMalloc
--define:useStdLib
--gc:arc
```
then benchmarked it with wrk like this:
```
wrk -t2 -c5 -d20s --timeout 2s http://localhost:9090
```

with all these setups, the server's process consumed 976.2MB of memory,
but when compile it with --gc:orc and the default one everything seems to be okay with a memory usage of 478KB and 4.4MB respectively.

The code is as below:
```nim
import jester

settings:
  port = Port 9090

routes:
  get "/":
    resp "Hello World"

runForever()
```

Tested on:
```shell
$ uname -a
Linux iMachine 4.15.0-134-generic #138-Ubuntu SMP Fri Jan 15 10:52:18 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
$ nim -v
Nim Compiler Version 1.5.1 [Linux: amd64]
Compiled at 2021-01-23
Copyright (c) 2006-2021 by Andreas Rumpf

```