Travis CI

This little buddy allows us to see, if a pull request would break the build.

Whenever somebody creates a pull request, TravisCI will pick it up in a couple of minutes, run the tests and mark the build as green or red. Only PRs where all commits have a green Travis build are ok to merge.

If there's an outage on Travis a local run of all tests is fine, but a comment should be made to say that all revisions have been checked and succeeded.