Add git pre-commit hooks

[eriknw]

Fixes #169.

@jim22k @ParticularMiner to use, first run

conda install -c conda-forge pre-commit
pre-commit install

To initiate a run:

pre-commit run --all-files

As the name "pre-commit hook" implies, these will also run automatically upon git commit command. See https://pre-commit.com/ for more detail.

This PR is a first attempt. We can modify hooks as desired.

Also, I removed the Black badge from the readme. I don't think it's special enough to call out anymore (we use lots of tools after all), and it has sufficient mindshare that we don't need to proselytize for it.

[coveralls]

Pull Request Test Coverage Report for Build 2175355044

• 43 of 43 (100.0%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 99.679%

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Totals
Change from base Build 2171171203:	0.005%
Covered Lines:	15155
Relevant Lines:	15185

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💛 - Coveralls