[WIP] Add Travis support

Especially with the possibility of Python 3 being added, having travis to run tests would probably be nice. There are issues with running the `ffi.verify()` after including cairocffi if the version of cairo is old, so I changed how the external ffi modules are imported based on a cairocffi example [1]. This is not ideal, but necessary to run Travis, since it's running 12.04, which has a very old version of cairo.

Current status: ![](https://travis-ci.org/flacjacket/qtile.svg?branch=travis)

[1] https://pythonhosted.org/cairocffi/cffi_api.html#example-using-pango-through-cffi-with-cairocffi