Merge pull request #78 from jcabi/master

merge to my repo
#751 MkContents.update(): improper usage of JsonPatch.patch()
Merge pull request #79 from jcabi/master

merge to my repo
Merge pull request #80 from jcabi/master

merge to my repo
Merge pull request #81 from lthuangiang/master

Merge pull request #80 from jcabi/master
Merge pull request #759 from lthuangiang/751

#759: pull request #751 MkContents.update(): improper usage of JsonPatch.patch()