AssociationScope no longer maintains state, so we're safe to keep a
singleton and save on GC time

Squashed commit of the following:

commit 96991e8e919edfb20cc4120bca4e36ed51175d57
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:29:24 2014 -0800

    Revert "gems can be added or skipped from the template"

    This reverts commit 8beb42cf.

    Conflicts:
    	railties/lib/rails/generators/rails/app/app_generator.rb
    	railties/test/generators/app_generator_test.rb

commit 35599c0e657245ef14ac0f28c9189ad16acf40e6
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:26:53 2014 -0800

    Revert "oops, template replay needs to happen after bundle. :orz:"

    This reverts commit 9104702b.

    Conflicts:
    	railties/lib/rails/generators/rails/app/app_generator.rb

commit f519c3902c313db8e906a49251c91643b8e6499e
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:25:51 2014 -0800

    Revert "only ask for these ivars if the target responds to them"

    This reverts commit 656d4125.

commit aa524a9428e3e4c45fe221f10a66a08efb827ab5
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:25:39 2014 -0800

    Revert "refactor generator tests to use block form of Tempfile"

    This reverts commit 65251820.

commit 7d3740549fa4dfa62e3761f8d4bc6d6d441256e7
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:25:25 2014 -0800

    Revert "add a more restricted codepath for templates fixes #13390"

    This reverts commit 2875b4a6.

commit 525df0af1001918986cdfce59539fd2d52c4f32c
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Fri Feb 14 11:25:11 2014 -0800

    Revert "add a send so `apply` can be called.  Fixes #13510"

    This reverts commit c5034d60.

Add verb to sanitization note

Fix path shown in mailer's templates

Add hint to error message of task db:migrate:down

Remove unused fixtures from sqlite3 test case

[Guides] fix guide active_support_core_extensions. add Note to String#indent [ci skip]

updated Travis build status image url

No variant should also be picked up by variant.any if variant.none is not defined (just like any other variant)

Check if variant array contains only symbols

Drop the correct index after reverting a migration

Dont use Enumarator on join_association

Variant negotiation

Previously when reverting a migration which added a named index it
would instead drop a corresponding index with matching columns but
without a name.

remove created state after test execution, not before the next test.
This prevents the leak of the `ex` table outside of a single test.

Allow setting `request.variant` as an array - an order in which they will be
rendered.

For example:

  request.variant = [:tablet, :phone]

  respond_to do |format|
    format.html.none
    format.html.phone # this gets rendered
  end

Cookies serializer improvements

do not crash when `config/secrets.yml` is blank.

Terminate the backend ourselves on PG 9.2+

This should make it harder to accidentally break this test.