Run the travis build in parrallel

http://about.travis-ci.org/blog/2012-11-28-speeding-up-your-tests-by-par
allelizing-them/
DB created in before_install
imagemagick part of the stack
Move the test suite variable to the front and make mysql a service
tidy up travis yml
formatting
Mysql is already running in travis

saves 3 seconds
Display is already set
set bundler_args: --without development
remove fog
Merge pull request #545 from alphagov/Run-travis-in-parallel

Run travis in parallel

Will keep an eye on it, and if it seems slower because of contention, we can revert back easily enough.