Simple support for literate coffeescript

Apparently, coffeescript comes with a literate variant -- http://coffeescript.org/#literate. This pull request implements simple syntax highlighting for it by using the markdown syntax and then including coffee syntax in it. I think there are some mismatches, but regrettably, I don't understand syntax highlighting a lot, so I'm not sure how to fix them. I may update the code if I figure it out.