Enable travis tests
Travis builds don't have SwapCached in meminfo
Add qtile Travis-ci status to README
Make Python 2.6 compatible

Dict comprehension and set literals are introduced in 2.7
Fix AttributeError recursion error
Fix test/test_command.py

Fix tests for commands added to CommandObject in
743a8a7be839bb1179580dd38f3e791ba7b839ab
Merge remote-tracking branch 'flacjacket/travis' into develop
We have packages for Saucy and Trusty too
Try to keep tests running

Make sure children of forks exit so we (hopefully) don't get fork bombs.

Use a temporary file for the qtile socket, so if things don't shutdown
nicely in one test, the following tests won't also fail.
Run scripts/window.py with current executable

Closes #453
Update bars on screens with a groupbox when window focus is changed. Fix for #451.