Added a build bot for Cabal

[Johan Tibell]

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