Fixed according to the discussion

Tested with failing code - compared the result and it matched what is in
TFS
Merge pull request #640 from voloda/Issue#632

#632: Need support for ExtendedMerge of type Delete
Update libgit2sharp to v0.19
Update rcheckin.md
Merge pull request #638 from pmiossec/update_libgit2sharp

Update libgit2sharp to v0.19
Use libgit2sharp to find commits to checkin
Adapt FindParentCommits() to return nothing when commits are not parents
Unit test