Use helper method to get ENV['CONTENT_LENGTH']
Use Request#raw_post instead Request#body

In order to get raw_post to be not empty after
ParamsParser#parse_formatted_parameters,
added rewinding of body stream input on parsing json params.

Closes #11345
cache.exists? should return true/false
Explicitly test for true and false.
Added cursor pointer for 'More Ruby on Rails'

dropdown menu on guides page (which appear on small windows)
[ci skip]
Fixed broken link of Travis CI for rails and added full path
Remove redundant test about `push_with_attributes` removal.
link break added after the Travis CI link

link break added after the Travis CI link
Merge pull request #11373 from vipulnsward/remove_deprecated_test

Remove redundant test about `push_with_attributes` removal.
Merge pull request #11368 from Amit-Thawait/master

Fixed Travis CI link for rails
Merge pull request #11361 from jetthoughts/add_cursor_pointer_for_menu

Added cursor pointer for 'More Ruby on Rails' dropdown menu on guides page (which appear on small windows)
Merge pull request #11353 from jetthoughts/revert_to_raw_post

Use Request#raw_post instead Request#body in ParamsParser#parse_formatted_parameters
Merge pull request #11351 from jetthoughts/cleanup_request

Use content_length method instead of ENV['CONTENT_LENGTH'].to_i
Merge pull request #11354 from jadeatucker/cache_exists_should_return_boolean

cache.exists? should return true/false