Bump version from 2.2.0 to 2.2.1

[DilumAluthge]

In preparation for a new release.

[DilumAluthge]

I'd like to get #1038 merged first.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.16%. Comparing base (c1f6bb8) to head (f0bf51e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1045   +/-   ##
=======================================
  Coverage   86.16%   86.16%           
=======================================
  Files           3        3           
  Lines         795      795           
=======================================
  Hits          685      685           
  Misses        110      110           

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