Now all branches will be tested by Travis.

This enables testing of all branches also on developer repositories which is very helpful for testing your PRs before actually submitting the PR to `ufz/ogs`. (so no more *DONT MERGE THIS PR* ...)

You have to enable Travis on your repository, see the [developer guide](http://docs.opengeosys.org/docs/devguide/testing/travis) how to do this.