#515 Tags implementation

RtTags, RtTag, MkTags, MkTag, plus unit and integration tests.
Merge branch 'master' into 515
#515 removed the puzzle
#515 fixes
#515 style fixes
#515 removes one time variables
#515 removed another one time variable
#515 put random names to the tags
Issue 585. RtReposITCase.create() @Ignore annotation and todo removed.
Issue 586. MkRepoCommitTest created
#515 removed redundant refsEntry field
#515 variable change in RtTagsTest
#515 iterate over entrySet instead of keySet in MkTags create()
Merge pull request #595 from amihaiemil/515

#595: pull request Pull request for #515
Issue 586. Fixes after code-review
Merge branch 'master' of github.com:aistomin/jcabi-github into Issue-586
Merge pull request #613 from aistomin/Issue-586

#613: pull request Issue 586. MkRepoCommitTest created
Merge pull request #612 from aistomin/Issue-585

#612: pull request Issue 585. RtReposITCase.create() @Ignore annotation and todo removed.
Merge remote-tracking branch 'upstream/master'