Displaying moonc version

`moonc -v`
```
Usage: /usr/local/lib/luarocks/rocks-5.4/moonscript/0.6.0-1/bin/moonc
       ([-t <output_to>] | [-o <o>] | [-p] | [-T] | [-b] | [-X]) [-h]
       [-l] [-v] [-w] [--transform <transform>] [-]
       <file/directory> [<file/directory>] ...

Error: missing argument 'file/directory'
```

Version mismatch (0.6 installed):
```
moonc -v ?
MoonScript version 0.5.0
```
