Travis CI integration

I made some changes so the project can be built by TravisCI. Namely:

* Add `.travis.yml` configuration file
* Move OBConnection dependency to Cocoapods
* Tweak code sign settings

If you want to enable TravisCI in your own repository, besides accepting this pull request, you must:

* Create an account in travis-ci.org using the `TheGossip` Github account (or any other account with write access yo GossipLeague)
* Enable travis hooks for GossipLeague
* Change the "Build status" image url in README.md to point to your own username