- Drop support for Python < 3.6 (including Python 2), resolves#94
- Some dependencies have less strict requirements, resolves#121
- Add Python 3.8 and 3.9 support
- Rebase Docker images on Python 3.9.4 and Alpine 3.13
- Update CI pipelines and remove Travis
- Update dependencies
- Update Linux Docker image to use Alpine 3.8
- Prepare for Python 3.7 in test matrices (not ready yet)
- Minor fixes and doc updates