Add badges support

[joaomdmoura]

In this new version of Gioco we should aim for a more clean architecture and also a more OO approach.

Let's keep it simple and start by adding badges support. The models should be pretty straightforward but the methods for adding, removing and updating badges should follow a OO-way and a Rails way by having the logic contained by its own class, instead of "random" methods injected on other existing classes.