Update Travis CI script.

Experimental PR to update the Travis configuration:

 - Get Travis working again on 2.6, 3.3 (see https://github.com/travis-ci/travis-ci/issues/2219)
 - Add Python 3.4.
 - Stop spamming @burnpanck.

I'm not sure how this will affect the UI tests; let's see what happens. :-)

Addresses #178.