Syntax highlighting

I implemented syntax highlighting for MyriaL. Please let me know if there are important parts missing.

@dhalperi suggested that the keywords should be exported from raco automatically. See https://github.com/uwescience/datalogcompiler/issues/185. At the moment the list of keywords is incomplete. 

![screen shot 2014-04-28 at 20 25 45](https://cloud.githubusercontent.com/assets/589034/2825454/f8e616da-cf4d-11e3-8876-206e8038f8dd.PNG)

FYI @7andrew7 and @dhalperi