Integrate with coveralls coverage reporting
Merge pull request #111 from alphagov/integrate-with-coveralls-clean

Integrate with coveralls coverage reporting
Run travis against master branch

We are moving towards using travis as the main CI system for backdrop.
In which case we should be running it against master as well.
Add build status image to README

Advertise how we're doing.
Merge pull request #112 from alphagov/run-travis-on-master

Run travis against master branch