style: Update to Black v20.8 formatting

[matthewfeickert]

* Apply Black v20.8b1 formatting
   - Should be similar to format of first stable release of Black
* Update Black pre-commit hook to use rev v20.8b1
   - Using pinned revs is the recommended approach for pre-commit: https://github.com/psf/black/issues/420

[codecov]

Codecov Report

Merging #16 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #16   +/-   ##
=======================================
  Coverage   90.90%   90.90%           
=======================================
  Files           3        3           
  Lines          11       11           
=======================================
  Hits           10       10           
  Misses          1        1           

Flag	Coverage Δ
#unittests	90.90% <ø> (ø)

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

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 97cc34c...5f25f08. Read the comment docs.