Separate JUnit code from core

[frankscholten]

Extract a core module that does not have a dependency on JUnit

[frankscholten]

Would be cool to have example tests that work with Spock

[sadovnikov]

Seems to be closed premature.

[sadovnikov]

There are a couple of thing remain after introduction of MesosClusterTestRule:

• the MesosClusterTestRule should move to a separated module;
• minimesos should lose compilation dependency on junit

[frankscholten]

Fixed after recent refactoring.