Added support for viewing compiled javascript as coffeescript

I was playing around and added CoffeeScript support to the site. I can understand if you don't want to pull this in, as it could be considered bloat. I tried to follow the styles in use, but let me know if find anything to be a code smell.

I will admit the mechanism for checking if the building of coffeescript should occur feels a little hackish and is too closely tied to the internals of the code-mirror editor, but I chose that route over alternatives.

I'm new to all this, so let me know if I've trodden all over some taboos or committed any faux pas. cheers!