Remove Travis builds for Python 2.6, 3.2, 3.3
Remove Travis builds for Python 2.6, 3.2, 3.3

It looks like Travis doesn't have installation archives for Python 2.6, 3.2, and 3.3 anymore, so let's just run the Travis builds on Python 2.7 and 3.4.  Also, python-nightly is no longer failing, so I removed the "allow_failures" declaration for that.
zestyping/q