update z3c.checkversions (0.4.1 -> 0.4.2)
update pytest (2.3.5 -> 2.4.2) and friends
fix awkward parameter naming in test setup
Add testbrowser real_login and real_logout helper methods

The other login and logout methods use basic authentication instead of
doing a real login.
Do real logins in functional tests

This does still not work due to missing test isolation.