CoffeeScript rewrite

Rewrote all the js code in CoffeeScript. Feels much cleaner now (and is much more fun :-)).

Please review @heipei
cc @rep 

This was basically my first CoffeeScript project, so please comment/critize.

I tested this with up-to-date versions of node and all the modules we use (and I had to do some minor changes in the server code to get it running), so before we merge this, we probably need to bump the version on the server, too.