Merged literate_coffee_script.lang from gist, fixing #30 and #27

As requested in #30 I've merged in `literate_coffee_script.lang` from [gist](https://gist.github.com/niclashoyer/4493699) by @niclashoyer.

With gists being git repositories on their own, I took the liberty of merging, such that @niclashoyer remains author in the history...
(gists are really awesome)

Back on topic, I'm not sure how well it recognizes `*.coffee.md` files, first time I opened a file with that name it was highlighted as markdown. However, when manually set it to "Literate CoffeeScript" it worked for all the other `*.coffee.md` files I opened afterwards.