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.
Remove conditional, since results are always an instance of `ActiveRecord::Result`
Added SanitizeHelper to rails guide docs [ci skip]

Added SanitizeHelper to rails guide docs [ci skip]

Added SanitizeHelper to rails guide docs update [ci skip]
Creating an SSE class to be used with ActionController::Live.
Added Action View in 'rake about' [ci skip]
added String#to_date documentation to Rails 4 upgrade guide

[ci skip]
Only cache template digests if config.cache_template_loading

since ActionView::Resolver.caching is set to the same value as config.cache_template_loading
only cache template digests if config.cache_template_loading is not falsy
fixes issues #10752 and #10791
Removing obsolete html tags in favor of markdown code block.
Revert "Removing obsolete html tags in favor of markdown code block"

This reverts commit 157dc275da0ad38635337b7c1d96de656d91de8e.
Minor align BR tags with HTML void - with reference to the generators code change - https://github.com/rails/rails/commit/f038d4cc5fe1ac21f92c7e32c61ff85a0c816f3f
use `skip` so we can see what tests are not run
Merge pull request #11331 from vipulnsward/remove_conditional

Remove conditional, results are always an instance of `ActiveRecord::Result`
cast hstore values on write to be consistent with reading from the db.
Set field encoding to client_encoding for mysql adapter.
Merge pull request #11802 from ko1/fix_field_encoding_for_mysql

Set field encoding to client_encoding for mysql adapter.
Remove using of suffix with term. [ci skip]
Merge pull request #11806 from jetthoughts/change_model_term_by_simple_word

Remove using of suffix with term. [ci skip]
Add tests for ActiveModel::Serializers::JSON#as_json ordering
Fix a broken link
Merge pull request #11815 from yaotti/patch-1

Fix a broken link [ci skip]