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
Improve the testing guide [ci skip]

Improve the "Testing Rails Applications" guide adding a section for
testing helpers and a little note about associations with ActiveRecord
and YAML fixtures.

Also add a link to Fixture Builder ; yet another replacement for
fixtures such as Machinist or FactoryGirl.
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.
cookies are encrypted starting Rails 4
doc for more input tag types
Complete a sentence in i18n guide's introduction

Add a list of what will be covered into this guide
Removed params permit step from 5.6 section [ci skip]
Document where `column` param gets utilized in `substitute_at`.
[doc] fixed printing of code samples
Removed redundant upgrade docs on new cookies.

[ci skip]
Merge pull request #11261 from ryan-endacott/fixguide

Removed redundant upgrade docs on new cookies.
Replaced older rocket sign to new :
Merge pull request #11295 from ankit8898/master

Replaced older rocket sign to new  ":"
SQL Keywords to be in UPPERCASE
Merge pull request #11297 from ankit8898/master

SQL keywords in UPPERCASE
Removed unsued deprecation require
Remove deprecated `ActiveRecord::Base.disable_implicit_join_references=`.
Removed deprecated `Rails.application.railties.engines`.
Merge pull request #11300 from arunagw/railties-engine-deprecation-removed

Removed deprecated `Rails.application.railties.engines`.
Merge pull request #11298 from raysrashmi/removed-deprecation-require

Removed unsued deprecation require