v0.9.0 - Fix Duo Web, Consistent user agent, Dropped old Python

• Fixes #64: Duo Web Failing
• Fixes #121: Use a consistent user agent
• Moves to using Black for formatting
• Adds pre-commit hooks
• Adds isort hook
• Adds testing for Python 3.10
• Corrects the supported versions list in setup.py
• Removes remaining Python. 2.x cruft
• Move to f-strings everywhere
• Start preparing for typing
• Improve/update CI
• Drops support for Python 2.7 and 3.5
• Adds support for Python 3.10