Added a GNU license

[Kronifer]

Saw that there was an open issue in your repo about a license, so added a License to your files.

[codecov-io]

Codecov Report

Merging #360 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #360   +/-   ##
=======================================
  Coverage   30.38%   30.38%           
=======================================
  Files          39       39           
  Lines        1277     1277           
=======================================
  Hits          388      388           
  Misses        889      889           

---

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 f6adf63...a47e4cb. Read the comment docs.