package cleanup

This series does:

• cleanup of the source for "proper" python packaging
• PEP8 cleanup
• minor code re-arrangement for clarity
• add pyproject.toml for distribution
• setuptools building of cli scripts
• setuptools-scm for versioning from git tags
• add GPL v3 license

After these changes, source distributions and wheels can be built with:

python3 -m build

Each commit should be able to be reviewed independently. If there are issues with any commit in particular let me know and I can adjust or drop as needed.