Enable unit tests on Python 3.5
Enable unit tests on Python 3.5

This enables the tests in tox and in Travis.  This ought to prevent
regressions in Python 3 support.

Note that Python 3.4 isn't supported (yet) because the vault code relies on
%-formatting of byte strings, a feature that was ripped out of Python 3.0
and restored in 3.5.

Also note that passing tests don't mean that Ansible itself can already
be used with Python 3.5: test coverage is only 53%.

thaim/ansible,thaim/ansible