Add python 3.5 to tox.ini test suite
Add python 3.5 to tox.ini test suite

Since there are python 3 versions in travis.yml, adding at least one here will make it easier to test python 3 compatibility in development.
jmwri/voluptuous,SimplyKnownAsG/voluptuous,SimplyKnownAsG/voluptuous,alecthomas/voluptuous,tuukkamustonen/voluptuous,divanovGH/voluptuous,tuukkamustonen/voluptuous,alecthomas/voluptuous