Include LICENSE in source and wheel

[hugovk]

Fixes #16.

[codecov]

Codecov Report

Merging #17 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #17   +/-   ##
=======================================
  Coverage   80.83%   80.83%           
=======================================
  Files           1        1           
  Lines         167      167           
=======================================
  Hits          135      135           
  Misses         32       32

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