CircleCI hash checking, test coverage, and test coverage badge

[JSchoenbachler]

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@5aaf2c9). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master      #3   +/-   ##
========================================
  Coverage          ?   0.00%           
========================================
  Files             ?       1           
  Lines             ?      20           
  Branches          ?       0           
========================================
  Hits              ?       0           
  Misses            ?      20           
  Partials          ?       0           

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