moonc cli needs to support args even when file is not included


```
leafo ~ > moonc -v
Usage: /home/leafo/.luarocks/lib/luarocks/rocks-5.1/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
```

```
leafo ~ > moonc -v blahblah
MoonScript version 0.5.0
```
