Update for 1.7.1 release

Add PyPI pyversions & license badges

Update for 1.6.4 release

Update for 1.6.3 release

Update for 1.6.2 release

Update for 1.6.1 release

Update release instructions to include `py37`,`py38`, and `doc` Tox envs

Update release instructions to mention testing via tox

Update for 1.5.2 release

Bump dev version