Brings this module up to date

In this PR:

* Adds tests
* No longer publishes coffee files to NPM (BAD! BAD! BAD!)
* Updates usage example to be in JavaScript
* Makes it work with any JADE version

Please publish to NPM. The code hasn't changed, so this can be published as a patch. If you'd like, please add me as maintainer to github and npm and I'll happily publish (I do this for many other modules).