Use mockito-core rather than mockito-all

mockito-core is packaged with an old version of hamcrest which conflicts with
JUnit 4.11, which means you can't use things like ExpectedException rules when you're depending on dropwizard-testing without explicitly excluding its mockito dependencies.

Just replacing mockito-core with mockito-all ends up with enforcer failures, because mockito-core depends on hamcrest 1.1 and JUnit 4.11 depends on hamcrest 1.3, but a bit of googling suggests that excluding the mockito-core dependency and running with hamcrest 1.3 works fine.