Fix typo in AS guide [ci skip]
Fix Calculations#pluck doc to mention several attributes can be selected [ci skip]
copy edits [ci skip]
Merge branch 'master' of github.com:lifo/docrails

Conflicts:
	guides/source/active_record_validations.md
Update documentation for javascript_include_tag [ci skip]
remove unneeded Examples tag [ci skip]
Improves documentation on favicon_link_tag
Removes :nodoc: label [ci skip]
nodoc AS::Testing::Pending because is deprecated [ci skip]
Remove :nodoc from SanitizeHelper module [ci skip]
nodoc AD & AV railties classes
Removes unneeded 'Example' tags and whitespaces [ci skip]
Removes :nodoc: tag on AtomFeedHelper [ci skip]
Improves documentation of Capture helper [ci skip]
Add documentation to TransactionIsolationError [ci skip]
Remove trailing whitespaces
Revert "Remove trailing whitespaces"

This reverts commit 90c887fa7d0c454b7533e208daefc342dea4d5f3.
Here's a few updates to the validations guide. A bunch of small changes,
plus:

* 80 column formats
* replacing the explanation of the dynamic_form gem with the example
  HTML/CSS that Rails scaffolds generate.
Merge pull request #8379 from steveklabnik/validations_guide

Validations guide
Migration Guide: General fix-up

This introduces a bunch of editing/re-writing to the migrations guide.
There were a bunch of small changes, and a few larger ones:

* mysql does support transactions.
* Add a section about db/seeds.rb
* Largely re-wrote the first few sections