Robinson foulds bug fix

[gloriayma]

Previously the check to see if a node is a leaf was degree(node) == 1, but this can mistakenly flag the root of the tree (which may have in degree 0, out degree 1, for a total degree of 1).

[codecov]

Codecov Report

❌ Patch coverage is 78.29181% with 61 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.39%. Comparing base (8b36987) to head (7e5df4e).
⚠️ Report is 16 commits behind head on master.

Files with missing lines	Patch %	Lines
src/cassiopeia/critique/compare.py	54.02%	40 Missing ⚠️
src/cassiopeia/data/CassiopeiaTree.py	92.15%	8 Missing ⚠️
src/cassiopeia/critique/critique_utilities.py	22.22%	7 Missing ⚠️
src/cassiopeia/plotting/deprecated.py	54.54%	5 Missing ⚠️
src/cassiopeia/data/utilities.py	97.05%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #283       +/-   ##
===========================================
+ Coverage   74.91%   85.39%   +10.47%     
===========================================
  Files          94       76       -18     
  Lines        8454     5914     -2540     
===========================================
- Hits         6333     5050     -1283     
+ Misses       2121      864     -1257     

Files with missing lines	Coverage Δ
src/cassiopeia/__init__.py	87.50% <100.00%> (ø)
src/cassiopeia/critique/__init__.py	100.00% <ø> (ø)
src/cassiopeia/data/Layers.py	83.78% <100.00%> (ø)
src/cassiopeia/data/__init__.py	100.00% <ø> (ø)
src/cassiopeia/mixins/__init__.py	100.00% <100.00%> (ø)
src/cassiopeia/mixins/errors.py	100.00% <ø> (ø)
src/cassiopeia/mixins/logging.py	100.00% <ø> (ø)
src/cassiopeia/mixins/utilities.py	100.00% <100.00%> (ø)
src/cassiopeia/mixins/warnings.py	100.00% <100.00%> (ø)
src/cassiopeia/plotting/__init__.py	100.00% <100.00%> (ø)
... and 66 more

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[colganwi]

Thanks for flagging this @gloriayma! I encountered the bug a few weeks ago and patched with #282. Just merge the 3.0.0 branch into your branch to get the patch.