Renamed class Node to TreeNode

[raajtilaksarma]

References to other Issues or PRs or Relevant literature

#34

Brief description of what is fixed or changed

Renamed all Node classes to TreeNode

Other comments

Did not create GraphNode class yet.

[codecov]

Codecov Report

Merging #35 into master will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##            master       #35   +/-   ##
=========================================
  Coverage   97.895%   97.895%           
=========================================
  Files           15        15           
  Lines          998       998           
=========================================
  Hits           977       977           
  Misses          21        21

Impacted Files	Coverage Δ
pydatastructs/utils/__init__.py	100% <ø> (ø)	⬆️
pydatastructs/trees/__init__.py	100% <ø> (ø)	⬆️
pydatastructs/trees/space_partitioning_trees.py	97.619% <100%> (ø)	⬆️
pydatastructs/utils/misc_util.py	100% <100%> (ø)	⬆️
pydatastructs/trees/tests/test_binary_trees.py	100% <100%> (ø)	⬆️
pydatastructs/trees/binary_trees.py	96.446% <100%> (ø)	⬆️

[czgdp1807]

No further work is needed. I will merge it after reviewing by tonight.

[czgdp1807]

Thanks.