Rhbz1124630 - remove RESTEasy dependency from client

by switching to jersey as JAX-RS implementation, in fedora we could save users 200MB download.

Depend on zanata/zanata-parent#36

Not really depend on this but it's nice to have (especially in preparation for Fedora packaging) zanata/zanata-api#22
The use of Mockito is an implementation detail which could change; I don't think it needs to be in the classname. Perhaps the `mock-server` module should be renamed - it isn't a mock object in the usual sense.