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
* Some other sections are obsolete
- Update classifiers
Change-Id: I73719cd22b52d9e35568d3d0e4e68846ab743522
License is now Apache + the original DataDog license,
i.e., dual licensing
Add the DataDog license and copyright to all files that have
the Apache license
Added that code was forked from Datadog's dogstatsd-python to
README.md
Change-Id: I90f1de2aad9f69316bf2cf44a00849d785c2bc64