Merge pull request #415 from msabramo/travis_use_tox

Travis use tox
Remove unused test_requirements.txt
This file was only referenced in .travis.yml and that reference was
removed in 52258069b7058fa1800177c9f33d3c699a95ef79.
Merge remote-tracking branch 'origin/master' into merge.py3k

Conflicts:
	test_requirements.txt