Setup build files for releasing plugin

[benmccann]

The plugin should be ready to be released after #127 is merged and the account is setup as described in the sbt docs

I believe the steps for each release will simply be:

• Release core library (the sbt plugin depends on the core library with same version number)
• Run sbt publish

I'm not quite sure how to test that this is setup correctly. I guess we will find out the first time we try

[codecov]

Codecov Report

Merging #125 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #125   +/-   ##
=========================================
  Coverage     90.86%   90.86%           
  Complexity      401      401           
=========================================
  Files            49       49           
  Lines           974      974           
  Branches        127      127           
=========================================
  Hits            885      885           
  Misses           58       58           
  Partials         31       31           

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[kobylynskyi]

@benmccann Awesome! Thank you for the instructions!