Replace middleman by Gulp

* Remove Middleman
* Add Gulp
* Scope JS with commonJS
* Remove Angular dependencies in tests
Not sure. By the way, it's already a configuration file and the only one we will need to configure the app.

I don't want to move it in another place because it means: write a Gulp task to generate the final file and I will have to build the website each time I want to run the tests.