Support of org.junit.TestRule

[fappel]

It would probably be a good idea to have rules support available to avoid reinventing the wheel - if possible. However I could not come up with an idea of how to support in particular rules that evaluate additional annotations on test methods.

[raner]

I can see how this could be challenging (or maybe even impossible) to solve in a rule, but in reality a lot of JUnit tests already use some kind of a non-standard runner (e.g., MockitoJUnitRunner, XtextRunner, etc.). Mockito luckily already has a rule alternative, and for Xtext I created one myself, but I'm sure there are other popular JUnit runners that don't come as a rule, so it would be really useful if Oleaster were available as a rule in those cases where another runner needs to be used at the same time.