added String#to_date documentation to Rails 4 upgrade guide

[ci skip]
defines a new :abort deprecation behaviour that raises

See the CHANGELONG message in the patch for further details.
fixes typo in CHANGELOG
renames the :abort deprecation behaviour to :raise

That is a better name, thanks @jeremy.
Add plural form example for AR I18n section [ci skip]
Merge pull request #11861 from sadjow/improve-doc-translations-active-record-models

Add plural form example for AR I18n section [ci skip]
using assert_not instead of refute
Merge pull request #11868 from rajcybage/fix_refute

using assert_not instead of refute
 #11804: Add description of action in Getting Started Guide

[ci skip]

Closes #11804
Updated outdated initialization guide [ci skip]
Add String#remove(pattern) as a short-hand for the common pattern of String#gsub(pattern, '')
Merge pull request #11847 from AJ-Acevedo/master

Updated outdated initialization guide [ci skip]
Merge pull request #11807 from jetthoughts/11804_actions_are_public_methods

Add description of action in Getting Started Guide [ci skip]
Generate namespaced routes correctly for generators. Fix for #11532
Merge pull request #11756 from zilkey/master

added String#to_date documentation to Rails 4 upgrade guide [ci skip]
test-case for fixed issue #11870.
Merge pull request #11544 from prathamesh-sonpatki/namespaced_routes_test

Generate namespaced routes correctly for generators. Fix for #11532