ActiveSupport::Notifications::Instrumenter#instrument should yield

Conflicts:
	activesupport/CHANGELOG.md

Cosmetic cleanup of generated Gemfile

based on a discussion with @rafaelfranca

- Remove obsolete/misleading comment about assets only being used production
- Remove unnecessary group :assets
- Eliminate blank lines if options[:skip_javascript] is not specified

Use define_method when method name contains weird characters.

Provides standard layout lookup behavior for method and proc cases

Conflicts:
	actionpack/CHANGELOG.md

entirelyby => 'entirely by'

When setting the layout either by referencing a method or supplying a
Proc there is no way to fall back to the default lookup behavior if
desired. This patch allows fallback to the layout lookup behavior when
returning nil from the proc or method.

drop errors constant

Fixed typos in activerecord

mention strong parameters in complex forms section of the guides.

Allow connection_handler to be overriden per-thread

Closes #9921.

See
https://github.com/wycats/thor/commit/08265a380d0ff3fce014e98e87bb8c2330858e4a
for the discussion and https://github.com/wycats/thor/pull/316 for the
fix

Drop variable assignment in validations

Restore columns dropped by hstore test

Disabling the hstore extension during testing created order dependent
test failures.

respect auto_increment in rename_column for mysql

Fixing some typo(s)/grammar.

Fixing some typos/grammar.

Asia/Ulaanbaatar is incorrect mapping

Fixes #9936

Adds support for concurrent indexing in PostgreSQL adapter

Bump TZInfo version to 0.3.37 based on version v2013b of the underlying tz data.

Adds support for algorithm option in MySQL indexes
Moves USING and algorithm options upstream

The syntax is still specific to the Adapter, so the actual executed string happens
in the corresponding adapter

use relative links inside guides [ci skip]

ActiveRecord::ConnectionAdapters::Column

See
https://github.com/rails/rails/blob/28b8ca766e3e7c6c43d3ae900c99f8377153c62/activerecord/lib/active_record/connection_adapters/column.rb#L16

move mailer testing examples into the testing guide.

Closes #9325.

I adjusted the example and the description in the testing guide and
simply linked from the mailer to the testing guide. This way we don't
have to maintain two separate places.