Fix Strong Parameters docs.

It's only possible to inherit from ActiveRecord::Base and not include
it.
Merge pull request #8338 from ugisozols/master

Fix Strong Parameters docs [ci skip]
correct css selector for the display of validation error messages: changed #error_explanation to #errorExplanation
No sort Hash options in #grouped_options_for_select
default source in Gemfiles to :rubygems rather than hardcoding the URL

* I guess this would be the preferrable default for Bundler
* current version of Bundler converts :rubygems into 'http://rubygems.org', not https://,
  and that will help those who are working on a very poor network environment that doesn't allow SSL
Merge pull request #8340 from skojin/grouped_options_for_select_without_hash_sort

No sort Hash options in #grouped_options_for_select
Merge pull request #8341 from amatsuda/bundle_source_rubygems

default source in Gemfiles to :rubygems rather than hardcoding the URL
Fix validation based on object not _id.

From https://github.com/rails/rails/issues/6161\#issuecomment-10750118
Adding a note about :inverse_of for validations.

From https://github.com/lifo/docrails/commit/cfd324b4b68469ba3188e4b7ba8586e59b239693\#commitcomment-2213592
Revert "Merge pull request #8341 from amatsuda/bundle_source_rubygems"

This reverts commit 33b29e0112db62d3a8c798bb58f51c0a839d9e26, reversing
changes made to ac8c729342e6b020a57d0d6887c8a8d5b39f96e0.

Reason:

https://github.com/rails/rails/pull/4684#commitcomment-920313
Add CHANGELOG entry for opt-out option of automatic template digesting
Cleanup CacheHelper changes allowing opt-out of cache digests

Instead of deleting the skip_digest option flag, this changes the method to merely check the
key. This change is because of a discussion in this thread:

https://github.com/rails/rails/pull/8317

This commit also makes #fragment_name_with_digest private due to its
functionality being subsumed by #cache_fragment_name.
Merge pull request #8339 from latortuga/cache-digest-opt-out-cleanup

Cache digest opt out cleanup
Merge pull request #8318 from Empact/fixture-file

Use File.join to better integrate fixture_path in fixture_file_upload.
prevent Dependencies#remove_const from autoloading parents [fixes #8301]
Use "refute" instead of "assert !"

Remove FIXME tag from abstract adapter test.
Clarifies the cookie store docs a bit and uses correct Markdown syntax for preformatted text
Revert "correct css selector for the display of validation error messages: changed #error_explanation to #errorExplanation"

At least in master the selector is snake case.

This reverts commit ba2fed41613e02bb6cfc46c92ace00abb99ce313.
Use assert_nil instead of assert_equal
Add comment to a table without model.

This table is being used to verify if the :limit options is being
ignored for text and binary columns