Issue 533. MkRepoCommits.compare() implemented.
Implementation
Merge branch 'master' into #589
Merge branch 'master' of github.com:aistomin/jcabi-github into Issue-553
#625 first round. added @NotNull almost everywhere
#625 second round. Added @NotNull to more methods
#625 Added rest of @NotNull

Also, put some puzzles and Ignored some tests.
Nullability test still stays ignored due to bugs.
#625 checkstyle fixes
Merge branch 'master' into 625
Merge branch 'master' into 625
#625 merge master into 625
#625 added @NotNull to mock classes
#625 checkstyle fixes
Issue 532: initial commit
#625 merged master into it
Merge pull request #637 from amihaiemil/625

#637: pull request Pull request for #625
Issue 533. MkCommitsComparison.repo() implemented. TODO removed.
Merge branch 'master' of github.com:aistomin/jcabi-github into Issue-553
Issue 533. Code formatting fixed.
Merge pull request #610 from aistomin/Issue-553

#610: pull request Issue 533. MkRepoCommits.compare() implemented.