Add support for freud 3.0

[chrisjonesBSU]

This PR fixes the breaking change in freud 3.0 (See #81). I also updated __version__.py to match the last release.

[chrisjonesBSU]

I still need to make sure the vectors are accounting for PBCs

[chrisjonesBSU]

Ok, should be ready to go. I want to test this out with GRiTS before merging, since the only change is to the cluster function.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.35%. Comparing base (3419258) to head (3f099cc).
Report is 6 commits behind head on master.

❗ Current head 3f099cc differs from pull request most recent head c563b7f

Please upload reports for the commit c563b7f to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #93      +/-   ##
==========================================
+ Coverage   96.33%   96.35%   +0.02%     
==========================================
  Files           8        8              
  Lines         791      796       +5     
==========================================
+ Hits          762      767       +5     
  Misses         29       29              

Files	Coverage Δ
cmeutils/gsd_utils.py	91.70% <100.00%> (+0.03%)	⬆️