Psautohint

- Dropped Python 3.6 support - Python 3.7 is now the minimum requirement
- Added Python 3.10 support
- Added `universal2` wheel for Mac (M1 support)
- Improved CI (including dropping use of `tox` for tests)
- Updated dependencies

- Updated for fontTools rounding changes (thanks, madig!)
([301](https://github.com/adobe-type-tools/psautohint/pull/301))
- Updated dependencies

- Fixed a major performance issue when hinting VFs (thanks, madig!)
([289](https://github.com/adobe-type-tools/psautohint/pull/289),
[221](https://github.com/adobe-type-tools/psautohint/issues/221))
- Updated dependencies
([290](https://github.com/adobe-type-tools/psautohint/pull/290),
[291](https://github.com/adobe-type-tools/psautohint/pull/291),
[292](https://github.com/adobe-type-tools/psautohint/pull/292))

- Removed unused third-party CI configs and related code
- Updated dependencies
- Removed deprecated CLI option flags that were temporarily in place for the autohint -> psautohint transition
- Removed `autohintexe` from Python wheels. It can still be built using `python setup.py build_exe`.
- Cleaned up Python code

- Move remaining CI workflows (building wheels, deploying) to GitHub Actions including building of Python 3.9 wheels for supported platforms.
- Updated dependencies
- Fixed some [minor formatting issues](https://github.com/adobe-type-tools/psautohint/pull/272)

- Mute ['unhinted <glyphname>' messages from tx](https://github.com/adobe-type-tools/psautohint/issues/231)
- Updated dependencies
- Generate coverage reports from GitHub Actions
- Fix [NULL pointer access when processing taito glyph](https://github.com/adobe-type-tools/psautohint/pull/263)
- Fix [dump-font.py utility](https://github.com/adobe-type-tools/psautohint/commit/e04a11844738584bb7a666fbb69ffb840b2d19ef) (thanks khaledhosny!)