* skip tests where one parameterize dimension was empty
* Fix Xfail does not work with condition keyword argument.
* Fix win32 path issue when puttinging custom config file with absolute
path in ``pytest.main("-c your_absolute_path")``.
* Fix maximum recursion depth detection when raised error class is not
aware of unicode/encoded bytes.
* Fix ``pytest.mark.skip`` mark when used in strict mode.
* Minor improvements and fixes to the documentation.
* Fix ``--fixtures`` to show all fixture definitions as opposed to just
one per fixture name.
While this makes things a little more complicated and means we'll need to use
`-r` to recreate tox environments, it has several advantages:
- Full support from requires.io (including PRs)
- Workaround for https://bitbucket.org/hpk42/tox/issues/332/ so we can update
virtualenv/pip
