Attempt at making Travis CI run UI tests using PyQt.
Only run UI tests on Python 2.7 using PyQt.

There is no easy way to install PyQt with Python 2.6 on Travis CI.
Travis CI did not pick up the ETS_TOOLKIT vlue from the script file.

Let's try this way instead.
Try to get Travis CI run the UI tests again.

I think I figured it out...
Merge branch 'travis-ui' into fix-tests