Releasing a new version

# run sanity checks
  tox
  make rcheck

# update the version in miepython/__init__.py
  git commit miepython/__init__.py -m 'update version' 
  git push

# update CHANGELOG.rst
  git shortlog v2.1.0..HEAD
  git commit CHANGELOG.rst -m 'update recent changes'
  git push

# create release tag on github
  git tag v2.1.0
  git push origin v2.1.0

# upload source to pypi
  python3 -m build
  python3 -m twine upload dist/*

# update/check releases
  open https://github.com/scottprahl/miepython
  open https://pypi.org/project/miepython/
  open https://miepython.readthedocs.io
