Reconfigure tox.ini

Update minversion of tox to 3.9.0 to support inline comments [1]

Move pep8 and coverage requirements to tox.ini

Fix typo in coverage job

[1] https://tox.readthedocs.io/en/latest/changelog.html#v3-9-0-2019-04-17

Change-Id: I3f39b25ee0fd44c1bc51f94a7fbee74de8cba65d
2 files changed