Make a few cleanups:
- Remove python 2.7 stanza from setup.py
- Add requires on python >= 3.6 to setup.cfg so that pypi and pip
know about the requirement
- Remove obsolete sections from setup.cfg:
* Wheel is not needed for python 3 only repo
- Update classifiers
Change-Id: I8f0436fe9f23e7b3671c1cf001bfab31b8f985e8
Andreas Jaeger