Modernization (3.8)

[coddingtonbear]

This brings this repo a little closer to the current standards including:

• Adds support for pre-commit (running black, mypy, etc, automatically).
• Adds github workflows integration for automatically running linters and tests.
• Drops use of 'six', many python 2.7 idioms, etc.
• Reformats the codebase using black.
• Misc other improvements.