Adding unit tests for vraptor-musicjungle

Adding some initial tests for vraptor-musicjungle.

May be ?
What you think to change to `assertThat(validation.getErrors(), empty())`? It's more readeable, sounds like "assert that validation.getErrors is empty". `empty()` is a static import from `org.hamcrest.Matchers`.

If the assert fails, hamcrest matchers have a more pretty message than `assertTrue` from JUnit, that don't show any message.