Add Github status to PR for c2go tests and warnings

[elliotchance]

This change is 

[codecov]

Codecov Report

Merging #338 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #338   +/-   ##
======================================
  Coverage    81.6%   81.6%           
======================================
  Files         142     142           
  Lines        6011    6011           
======================================
  Hits         4905    4905           
  Misses        886     886           
  Partials      220     220

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[elliotchance]

Reviewed 2 of 2 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

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