Removed TODO from 3 files

[Riyagoel2]

References to other Issues or PRs or Relevant literature

Closes #133

Brief description of what is fixed or changed

Other comments

[codecov]

Codecov Report

Merging #141 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #141   +/-   ##
=========================================
  Coverage   98.176%   98.176%           
=========================================
  Files           21        21           
  Lines         1590      1590           
=========================================
  Hits          1561      1561           
  Misses          29        29           

Impacted Files	Coverage Δ
pydatastructs/graphs/algorithms.py	100.000% <ø> (ø)
pydatastructs/trees/binary_trees.py	96.894% <ø> (ø)
pydatastructs/trees/space_partitioning_trees.py	97.619% <ø> (ø)