Purpose: so that devs can use tox to run v1 or v2 of ansible with various versions of python.
For example `tox -e py27-v2 will run python2.7 on v2. Currently, only py26 and py27 are run on v1 when
running just `tox` so that we aren't breaking builds.
Add tox integration to run unittests in supported python releases.
Travis-CI is used for test execution.
Additionally, the unittest TestQuotePgIdentifier was updated to support
using assert_raises_regexp on python-2.6.
Sample travis-ci output available at
https://travis-ci.org/ansible/ansible/builds/54189977