Added a build bot for Cabal

Hi all, Prompted by a regression due the GhcOptions refactoring (which was otherwise great) I've created a build bot for Cabal in hope to encourage people to add unit tests. The build bot lives on my VPS here: http://ci.johantibell.com/ I've set up the build bot to send an email to this mailing list if any tests start failing. Please add more tests! P.S. I had to disable two unit tests that have been failing for ages to get the build bot up and running. -- Johan