Added Broccoli build tool and bower to manage dependencies
Removed customised styles and adapted demo to Broccoli build tool

I removed the customised styles because they aren't needed anymore and
adapted `index.html` to Broccoli build tool; moreover, I updated
`demo/app.js` to make it works with Angular 1.2 release
Removed `libs` old folder used to keep vendor libs
Brocfile.js cleaned up