Preocts 20220612 pyproject

[Preocts]

Round two of pyproject.toml upgrade. This time we are using flit as the build engine as it seems smoother with the toml config than setuptools.

This change moves all configs into pyproject.toml to see what all the hype is about.

• flake8 args added to pre-commit-config because flake8 doesn't support pyproject.toml
• point of entry script added, this now installs with pip install . (that's neat)
  Cleaned up readme and added notes

[Preocts]

closes #3
closes #5