Improve js written for guides

* Stop using unnecessary global variable
* Use function defined by jQuery for simplicity
* Fix event listner for "more info button" to handle
  event on resize browser
Add few information about missing steps [ci skip]

Add some deprecations previously note covered such as the confirm
option for the link_to helper or options which aren't needed anymore

Also add a mention about the config.assets.js_compressor option.
Document where `column` param gets utilized in `substitute_at`.
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
use latches rather than mucking with the scheduler
if we remove the connection from the pool, we should close it
remove dead code
close our connection when we are done
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