Refscan

- Simplify using `black` to format the code base
- Refine a few sections of `README.md`

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.9...v0.1.10

- Add `--no-scan` CLI option that skips the database scanning step (i.e. only generate `references.tsv`)
- Extract `any_of`-processing code into a helper function to facilitate testing
- Add unit test that demonstrates how `refscan` treats the `any_of` constraint

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.8...v0.1.9

- Use different colors for zero versus nonzero violation counts in summary section

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.7...v0.1.8

- Measure test coverage

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.6...v0.1.7

- Added unit tests
- Formatted source code using `black`

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.5...v0.1.6

- Add screenshot to `README.md`

**Full Changelog**: https://github.com/microbiomedata/refscan/compare/v0.1.4...v0.1.5