Merge pull request #36 from jcabi/master

merge from master to my repo
Merge pull request #38 from jcabi/master

merge from master to my branch
Issue #308 - Implemented the iterate() method MkPublicKeys
Merge pull request #373 from lthuangiang/308

#373: pull request Issue #308 - Implemented the iterate() method MkPublicKeys
Merge remote-tracking branch 'upstream/master'