CoffeeScript support

```
$ cat main.litcoffee
Let's print:

    console.log 'bla!'

$ bin/browserbuild -m main main.litcoffee
...require.register("main.litcoffee", function(module, exports, require, global){
// Generated by CoffeeScript 1.6.2
(function() {
  console.log('bla!');

}).call(this);

});var exp = require('main');if ("undefined" != typeof module) module.exports = exp;else main = exp;
})();
```