Center list and Client list Unit Tests GCI: 5274556356886528

GCI: 5274556356886528 Task completed.

As the android studio 1.0 has been realeased, I've updated the gradle version that uses the project. Furthermore, I changed the .travis.yml configuration, because I've realised that it wouldn't pass the build unless specifing the Build Tools Version in the complete form (20.0.0) not only the first number version. I think that has changed a few days ago, when the repo started to fail on the CI builds.

P.S. I've tried squashing, but somehow I can only squash the last two commits, and when I push them, I lost the "squashing".