Update yeoman prompt to use Inquirer (Fix #228)

That's a PR following #228 discussion.

So, I created a separated module to handle prompt types ([Inquirer](https://github.com/SBoudrias/Inquirer.js)) with some option to validate and filter the user input. It is based upon Readline node API, so this allow realtime CLI update and acting on keypress events.

Right now, it is implemented in the beta [BBB generator](https://github.com/backbone-boilerplate/generator-bbb) and it's working great over there.

Feel free to discuss if you feel any features went missing or would be great add-on.

---------------------------------------------------
_I didn't take time to completly remove the old prompt system. I guess this should be done in the future or before merging this one._