Add a Gitter chat badge to README.md

[gitter-badger]

arvenil/kata now has a Chat Room on Gitter

@arvenil has just created a chat room. You can visit it here: https://gitter.im/kata型/community.

This pull-request adds this badge to your README.md:

If my aim is a little off, please let me know.

Happy chatting.

PS: Click here if you would prefer not to receive automatic pull-requests from Gitter in future.

[codecov]

Codecov Report

Merging #1 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #1   +/-   ##
=======================================
  Coverage   82.79%   82.79%           
=======================================
  Files          12       12           
  Lines         215      215           
=======================================
  Hits          178      178           
  Misses         21       21           
  Partials       16       16           

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