Remove rng references in tests issue40

[dylan-asmar]

A lot of tests depended on specific states and problems (e.g. rock positions). I removed use of a specific rng that "forced" some of these specific states and problems and instead dictated the specific problems or states where needed.

For the CI, removed the tests for macOS and windows. There should not be an OS specific issue with this package. If needed/desired, we can add back in. I also added tests for LTS of Julia in addition to the latest.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.89%. Comparing base (3deaf60) to head (8bb09e5).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #41   +/-   ##
=======================================
  Coverage   93.89%   93.89%           
=======================================
  Files           8        8           
  Lines         262      262           
=======================================
  Hits          246      246           
  Misses         16       16           

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[zsunberg]

Thanks @dylan-asmar !