Valiant

General housekeeping

- Configured tests to use Python 3.8 and 3.9
- Improved GitHub Actions
- Tidied up tests
- Updated dependencies

Fixed issue with new PyPi metadata fields causing parsing to fail.

Fixed:

- [4](https://github.com/pomes/valiant/issues/4):
Configure cache database to be stored in the cache_dir

Added:

- [5](https://github.com/pomes/valiant/issues/5)
Allow for configuration from file-based settings
- [6](https://github.com/pomes/valiant/issues/6)
Provide plugin model for report providers

Initial release