Fixing a small bug in the alias handling code

[jtatum]

Adding an alias properly substituted the correct language parser, but there is still a file filter that used only the known list of extensions. Added any alias to the extension list.

[jtatum]

Incidentally, I started to add test cases, but there is too much module level code in cli.coffee. It would either need to be substantially rewritten, or there would need to be a harness for running bin/sloc inside a specfile.

[flosse]

@jtatum You're right, we should clean up an rewrite the cli with specs. So feel free to improve that dirty code ;-)

[jtatum]

That would be in a separate pull request for sure :)

[flosse]

ok