Depend on mockito-core instead of mockito-all in the integration test projects.
Additionally, exclude dependency on org.hamcrest:hamcrest-core.

This fixes test failures on Kepler caused by conflicting versions of
hamcrest-core present on classpath: version 1.1 embedded in mockito-all and
version 1.3 pulled in as P2 dependency.
Merge pull request #453 from rkrzewski/kepler-tests

Depend on mockito-core instead of mockito-all in the integration test projects.