Add `tox.ini` config with supported versions, and a new tox CI
workflow to run tox tests on master branch changes. This is "expensive"
so we may consider limiting execution further.
* Make `build_examples.py` callable from python
* Allow tests to run from outside project directory
* Add invoke tasks
* Add server tests
* Run travis tests against wheel package instead of local code
* Update `badge.write_badge()` to support `pathlib.Path`
* Update `CONTRIBUTING.md`
- Add .pre-commit-config.yaml with initial config.
- Add python black pre-commit config
- Apply pre-commit code changes
- Add information to CONTRIBUTING.md
- Add pre-commit to build requirements
- Run pre-commit during travis CI build
- Use a travis build matrix to control when pre-commit runs
in the CI process. Use explicit include to only run
pre-commit on Python 3.9.
* Stop using Mr Bump for version handling.
* Only deploy to pypi on tags (not master branch).
* Pick up version number from Travis CI TRAVIS_TAG environment variable.
