don't log errors when all is fine
Small Action View Overview edits [ci skip]

Some small grammar and readability edits
[ci skip] Document PublicExceptions middleware
[ci skip] document ActionDispatch::FileHandler
[ci skip] Document ActionDispatch::Static
Uppercase HTML in docs.

[skip ci]
Small grammar fix in pluck description
Correctly determine if migration is needed.

This method would assume that if last migration in the migrations
directory matched the current schema version, that the database was up
to date, but this does not account for new migrations with older
timestamps that may be pending.
`overriden` => `overridden`
[ci skip] Update links in getting_started guide.
Define the Duration#instance_of? method

Since Duration is extending from ProxyObject which extends itself from
BasicObject, the Duration object doesn't respond to the #instance_of?
method. Thus, the #method_missing hook get triggered, delegating the
method to its `value` attribute.

However, Rubinius' #eql? definition relies on #instance_of?, thus this
will equal to true with a Fixnum (since its `value` attribute is a
Fixnum) while it should not.

The previous behavior was wrong anyway, no matter the implementation.
fix broken link [ci skip]
Merge pull request #16546 from aditya-kapoor/remove-broken-link

fix broken link to rails blog [ci skip]
Add activejob guide to documents.yml [ci skip]
Merge pull request #16539 from seuros/activejob

[ActiveJob] Add queue_name_prefix
Merge pull request #16547 from cristianbica/add-active-job-guide-links

Add activejob guide to documents.yml [ci skip]
Fixes the `Relation#exists?` to work with polymorphic associations.

Fixes #15821.
Fix broken link to Upgrading Ruby on Rails Guide

in the 4.2 Release Notes [skip ci]

Change to link suggested by @zzak [skip ci]
Merge pull request #16545 from jonatack/patch-9

Fix broken link to Upgrading Ruby on Rails Guide [ci skip]
Grammar pass

[ci skip]

Add improvements from @eileencodes [skip ci]