Mapping support

These commits add an additional option to create map files.
More information about map files can be found on [here](http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/) and [here](http://coffeescript.org/#source-maps).

It works fine for me but since there are no unit tests, I'm not be too sure I didn't break anything. Please test all commands **before merging**. I don't have test cases for `docs` and `test`.