Add Code Coverage Reporting

[Furchin]

Use the CircleCI build to publish code coverage metrics to both coveralls and codecov.

[coveralls]

Changes Unknown when pulling f8ec18e on mbryc-codecoverage into ** on master**.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@e176000). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             master     #2   +/-   ##
=======================================
  Coverage          ?   100%           
=======================================
  Files             ?      6           
  Lines             ?     33           
  Branches          ?      0           
=======================================
  Hits              ?     33           
  Misses            ?      0           
  Partials          ?      0

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[coveralls]

Changes Unknown when pulling 66e84dd on mbryc-codecoverage into ** on master**.