Add {posargs} to tox.ini
Add {posargs} to tox.ini

This lets us pass arguments to pytest while using tox.
http://tox.readthedocs.io/en/latest/example/general.html

e.g., we can run just some of the tests:
    tox -e py36 -- -x test/test_manager.py

qtile/qtile,zordsdavini/qtile,frostidaho/qtile,soulchainer/qtile,ramnes/qtile,tych0/qtile,kynikos/qtile,frostidaho/qtile,ramnes/qtile,cortesi/qtile,tych0/qtile,zordsdavini/qtile,kynikos/qtile,flacjacket/qtile,cortesi/qtile,flacjacket/qtile,qtile/qtile,soulchainer/qtile