Add new lexeme regex.
Replace previous font-lock defaults with new.
Fix bugs & remove old code.

100% test passage here.
Fix attribute highlighting regex.
Change fontify-atoms test to expected failure.
Add test for fontification of map keys.
Fix deprecated font face reference.

Apparently font-lock-reference-face is an alias for font-lock-constant-face.

The former has been deprecated since emacs 20. This would explain why I couldn't
get the "right" font face to show up for atoms and map keys.
Add custom atom & attribute faces.

I am aware these are probably unbelievably hideous. Please forgive me.
Fix copy-pasta'd font face documentation.
Merge pull request #91 from elixir-lang/lexeme-regex-updates

Updates to regexes for various lexemes