Add tox env for Python 3.3 with 3rd party libs
Add tox env for Python 3.3 with 3rd party libs

This additional tox environment, py33-3rd-party-libs, runs the tests on
Python 3.3 where the 3rd party versions of the distutils2 and mock
libraries are installed rather than using the matching libraries from
the standard library.

osupython/pip2