add black to pre-commit and github actions

[alxndrkalinin]

closes #57

This PR:

• adds black config black.toml
• makes black run locally on commit via pre-commit
• adds black to github actions

[alxndrkalinin]

@gwaygenomics Another suggestion is to also add flake8 to enforce style, like no unused imports, missing docstrings, etc. Wdyt?

[codecov-commenter]

Codecov Report

Merging #70 (e6073f5) into master (3c907ea) will increase coverage by 0.06%. The diff coverage is 96.55%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   98.87%   98.93%   +0.06%     
==========================================
  Files          33       33              
  Lines        1064     1032      -32     
==========================================
- Hits         1052     1021      -31     
+ Misses         12       11       -1     

Flag	Coverage Δ
unittests	98.93% <96.55%> (+0.06%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cytominer_eval/__about__.py	100.00% <ø> (ø)
cytominer_eval/evaluate.py	100.00% <ø> (ø)
cytominer_eval/operations/enrichment.py	100.00% <ø> (ø)
cytominer_eval/operations/grit.py	100.00% <ø> (ø)
cytominer_eval/operations/hitk.py	95.23% <ø> (ø)
cytominer_eval/operations/mp_value.py	100.00% <ø> (ø)
cytominer_eval/operations/precision_recall.py	100.00% <ø> (ø)
...miner_eval/operations/replicate_reproducibility.py	100.00% <ø> (ø)
cytominer_eval/tests/test_evaluate.py	100.00% <ø> (ø)
...iner_eval/tests/test_operations/test_enrichment.py	100.00% <ø> (ø)
... and 18 more

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[alxndrkalinin]

@gwaybio Finally back to this. I tested linting with flake8 under python versions 3.5-3.9 and the requirements seem consistent.

New changes make code flake8-compliant – mostly removing unused imports, variables, etc. It's not checking for docstring formatting, because it produces a ton of small issues – like only single-line docstring is allowed at the top of the file – I'm not sure are that important at this point.