algo(louvain): fix self loop handling, configure threshold

[sdht0]

Answers now match with grappolo for soclj when they were previously not.

Added a new optional parameter tolerance.

Running some more tests on other graphs.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.79%. Comparing base (c567b0d) to head (5e1de0d).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5381   +/-   ##
=======================================
  Coverage   86.79%   86.79%           
=======================================
  Files        1413     1414    +1     
  Lines       62006    62037   +31     
  Branches     7607     7611    +4     
=======================================
+ Hits        53816    53843   +27     
- Misses       8015     8019    +4     
  Partials      175      175           

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