Difference in compiler behavior with -d vs --outdir
Contrary to the assertion in the help text, the `-d` and `--outdir` switches seem to do different things:
```
$ ksc --version
kaitai-struct-compiler 0.7
$ ksc -t cpp_stl -d ~/tmp/ DjidatV3/Records/djidat.V3.Template.ksy 
[residual] arg = '/Users/scalesw/tmp/'
[residual] arg = 'DjidatV3/Records/djidat.V3.Template.ksy'
# Executing command line:
java
-cp
/opt/kaitai-struct-compiler-0.7/lib/io.kaitai.kaitai-struct-compiler-0.7.jar:/opt/kaitai-struct-compiler-0.7/lib/org.scala-lang.scala-library-2.11.7.jar:/opt/kaitai-struct-compiler-0.7/lib/com.lihaoyi.fastparse_2.11-0.4.1.jar:/opt/kaitai-struct-compiler-0.7/lib/com.lihaoyi.fastparse-utils_2.11-0.4.1.jar:/opt/kaitai-struct-compiler-0.7/lib/com.lihaoyi.sourcecode_2.11-0.1.1.jar:/opt/kaitai-struct-compiler-0.7/lib/org.yaml.snakeyaml-1.16.jar:/opt/kaitai-struct-compiler-0.7/lib/com.github.scopt.scopt_2.11-3.4.0.jar
io.kaitai.struct.JavaMain
-t
cpp_stl
/Users/scalesw/tmp/
DjidatV3/Records/djidat.V3.Template.ksy

/Users/scalesw/tmp (Is a directory)
$ ksc -t cpp_stl --outdir ~/tmp/ DjidatV3/Records/djidat.V3.3.ksy 
$
```
