Code coverage improvements

[benank]

• Fixes code coverage comments in PRs (see below)
• Blocks merging PRs if coverage goes down (any code added must have UTs)
• Adds Python 2.7 code coverage (unsure of how this is working right now - will require more time later to investigate)
• Does not block merging if tests are failing - will need to investigate more on that later

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@8392668). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #120   +/-   ##
=========================================
  Coverage          ?   80.05%           
=========================================
  Files             ?       86           
  Lines             ?    11549           
  Branches          ?        0           
=========================================
  Hits              ?     9246           
  Misses            ?     2303           
  Partials          ?        0           

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