[WIP] Added algorithms for lowest common ancestor in BinaryTree

[czgdp1807]

References to other Issues or PRs or Relevant literature

[1] https://en.wikipedia.org/wiki/Lowest_common_ancestor
[2] https://pdfs.semanticscholar.org/e75b/386cc554214aa0ebd6bd6dbdd0e490da3739.pdf

Brief description of what is fixed or changed

Algorithm for lowest common ancestor has been added. A work in progress.

Other comments

[codecov]

Codecov Report

Merging #27 into master will increase coverage by 0.095%.
The diff coverage is 100%.

@@              Coverage Diff              @@
##            master       #27       +/-   ##
=============================================
+ Coverage   97.761%   97.857%   +0.095%     
=============================================
  Files           15        15               
  Lines          536       560       +24     
=============================================
+ Hits           524       548       +24     
  Misses          12        12

Impacted Files	Coverage Δ
pydatastructs/trees/tests/test_binary_trees.py	100% <100%> (ø)	⬆️
pydatastructs/trees/binary_trees.py	97.382% <100%> (+0.255%)	⬆️

[czgdp1807]

In accordance with our PR policy, closing this PR for now and creating a new issue for it.