title: Automatic merge branch into master on successful build in travis
body: <p>I've trying to do a setup, where I use Travis CI
  (<a href="http://www.travis-ci.org">http://www.travis-ci.org</a>) to build and test my program each time I commit to GitHub. My GitHub setup is to have a master and a slave/test branch, which I commit to before merging into master. However, as of right now I'm doing the merging manually on GitHub.com, which I could like to automate, such that when a build is successful on Travis, I want to merge my slave/test branch into the master right away. Does anybody know how this is possible on Travis CI or another way of achieving this with Travis?  </p>