Adding continuous integration using travis-ci.org

Addition of .travis.yml in order to integrate travis-ci infrastructure.
What would be required then would be to link a travis account to the Github JFXtras/jfxtras-labs repository. This must be done by a member of the JFXtras community github project because right access is required so that Travis can register a pull hook. I would be able to do it I think if someone could add me to the JFXtras github community.

The build from travis is correctly working as shown on the ci-build of my fork : https://travis-ci.org/McFoggy/jfxtras-labs

Next step would be then to add automatic snapshot deployment, but it is another story.