git: support readme configuration

[joyeecheung]

Also fixes the status code handling in git-node.

Fixes: #212

[codecov]

Codecov Report

Merging #223 into master will decrease coverage by 4.09%.
The diff coverage is 44.44%.

@@            Coverage Diff            @@
##           master     #223     +/-   ##
=========================================
- Coverage    92.1%   88.01%   -4.1%     
=========================================
  Files          18       19      +1     
  Lines         659      701     +42     
=========================================
+ Hits          607      617     +10     
- Misses         52       84     +32

Impacted Files	Coverage Δ
lib/run.js	21.62% <100%> (ø)
lib/cli.js	51.42% <33.33%> (+0.7%)	⬆️
lib/pr_data.js	91.52% <40%> (-4.84%)	⬇️

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[priyank-p]

Great, work.