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* Drop Python 2 support.
* Minor updates to package metadata.
* Update docs build, use readthedocs v2 configuration.
* Simplify package maintainence and tooling. `tox` removed. `flake8` replaced for `ruff`. Testing now just `ruff` and `pytest`.
* Switch from setup.py to pyproject.toml with hatchling for builds and an /src layout.
* Remove Travis CI integration and configurations in favor of Github Actions.