Adds the get contents operation

[fedefernandez]

Fixes #79 by adding the getContents operation

Please @juanpedromoreno could you review? Thanks

[juanpedromoreno]

LGTM!

[codecov-io]

Codecov Report

Merging #80 into master will increase coverage by 0.28%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
+ Coverage   79.47%   79.75%   +0.28%     
==========================================
  Files          35       35              
  Lines         492      499       +7     
  Branches        2        2              
==========================================
+ Hits          391      398       +7     
  Misses        101      101

Impacted Files	Coverage Δ
...c/main/scala/github4s/free/domain/Repository.scala	100% <ø> (ø)	⬆️
...in/scala/github4s/free/algebra/RepositoryOps.scala	75% <100%> (+3.57%)	⬆️
...4s/shared/src/main/scala/github4s/GithubAPIs.scala	96.15% <100%> (+0.32%)	⬆️
...cala/github4s/free/interpreters/Interpreters.scala	83.01% <100%> (+0.32%)	⬆️
...b4s/shared/src/main/scala/github4s/api/Repos.scala	95.65% <100%> (+0.65%)	⬆️
...ub4s/shared/src/main/scala/github4s/Decoders.scala	95.83% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 911188f...4cc2153. Read the comment docs.