Auto-deploy the Talkilla repo to the staging server

This is based on http://neilmiddleton.com/deploying-to-heroku-from-travis-ci/ and the encryption hints from http://stackoverflow.com/questions/9338428/using-secret-api-keys-on-travis-ci.

What we're doing is telling Travis CI to push to git, only on success, and only if this isn't a pull request, and only if it is a push to the master branch.

The key is encrypted and is tied to the master github repo.

I've tested this with slightly different repo settings on my repo and it seemed to work fine.

I think anyone can review this as it is just build integration.