Adding unit tests for vraptor-musicjungle

Adding some initial tests for vraptor-musicjungle.

May be ?
So... `UserBuilder` extends `User`. I think that `UserBuilder` creates a `User`, but isn't a `User`. What you think about?

I think that `UserBuilder` can be changed use composition over inheritance, and returning object with `build` method like: `new UserBuilder().withXYZ().build()`.