Validate with Travis CI

Run `scripts/validate.py` on [Travis CI](https://travis-ci.org/). This is triggered by pushes to branches and pull requests. Also added a build passing/failing icon in README linking to the Travis CI builds.
Can we pin this to 1.1.0 (same as we do on the puppetmaster)?
https://github.com/ocf/puppet/blob/master/modules/ocf_puppet/manifests/puppetmaster.pp#L6