Refactored the storage of a temporary version of the local cache into
its own method.
Merge pull request #10254 from wangjohn/refactoring_local_cache

Refactored the storage of a temporary version of the local cache.
The increment and decrement commands in the local cache are exactly the
same, so their logic is being refactored.
Merge pull request #10255 from wangjohn/increment_or_decrement_refactoring_in_local_cache

Refactoring increment and decrement in local cache
Use secure source for rubygems in engine tests
Merge pull request #10259 from prathamesh-sonpatki/secure-engine-tests

Use secure source for rubygems in engine tests
Let the paragraph about 'unobtrusive javascript'  more  explanatory
Add events reference link to the text about jquery-ujs.