Give Chris badges

[jonseitz]

Adds badges for build status, code coverage, documentation (just a link), and top language -- all keyed to our master branch.

I opted for shields.io over the native travis/codecov versions so that we could enforce consistency.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have run eslint on the code
• [x] I have added JSDoc for all of my code (where applicable)
• [x] I have added tests to cover my changes.

Priority:

• [ ] Normal
• [x] High

Related Issues:

Fixes #___

[codecov[bot]]

Codecov Report

Merging #9 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #9   +/-   ##
=======================================
  Coverage   94.52%   94.52%           
=======================================
  Files          12       12           
  Lines          73       73           
  Branches        6        6           
=======================================
  Hits           69       69           
  Misses          3        3           
  Partials        1        1

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