Looks like there are no problems with Python 3.6 yet. We make it a
regular target in tox and will start official support in `setup.py`
after a while.

Use of ``[pytest]`` section in `setup.cfg` is deprecated while
the new section name ``[tool:pytest]`` is not recognized by older
`pytest` versions.

To stay compatible with older `pytest` and avoid warnings with
`pytest` 3.0+, we move the whole config to `tox.ini`, where still
the old section name is valid.

`pip`, `wheel` and other fundamental helpers dropped or are going
to drop py3.2. It makes no sense to stick with it.

We pin py.test to version < 2.8.0 to make it work with the
`--doctest-modules` option enabled. We still wait for this bug
in py.test being fixed (announced in issue tracker for 2.8.3
release of py.test).