Use Travis CI to run tests

This adds `.travis.yml` file, to actually get the upstream repo on Travis just visit [travis-ci.org](http://travis-ci.org) and click _Sign-in with GitHub_ it will then show a list of your repositories - all very easy and free actually.

Here is the [first build](http://travis-ci.org/#!/errordeveloper/contrib-californium/builds/2224156) of my fork!

Once enabled travis will test on push or pull-request.