Drop 2to3, make python files 2/3 compatible.

This should be all the changes needed to avoid needing 2to3, I had this pass all tests on 2.7 and 3.4, and pylint --py3k returns no errors.

Note that this includes the adding py34 to tox commit, as I was using it find all the incompatibilities, and I wasn't sure how to pull it out.