:nail_care: for migrations guide from #15457 [ci skip]
Avoid looping through subscribers when unsubscribing with a subscriber object.
New records should remain new after yaml serialization
Merge pull request #15444 from sgrif/sg-yaml-new-record

New records should remain new after yaml serialization
Feature requests should be made on the mailing list, not submitted to
the issue tracker. See also #15455 [ci skip]
pg, inline casting methods into `OID::Type` objects.

This inlines casting for the most obvious types. The rest will
follow eventually. I need to put some tests in place, to make sure
that the inlining is not causing regressions.

/cc @sgrif
test pg, add basic test cases for point datatype.
docs, fix typo [ci skip]
[ci skip] fix "note" syntax
[ci skip] less derogatory explanation of defaults
[ci skip] add fixture docs link to guides

The fixtures API docs are really comprehensive. We should either be driving people there, or perhaps making fixtures its own guide.
[ci skip] explain association behavior. 

When you manually specify `id:` attribute in a fixture Rails' built in association assignment feature will no longer work. http://stackoverflow.com/questions/23985675/incorrect-association-in-fixtures

This commit raises awareness of this behavior and encourages developers to look directly at the fixture documentation.
Merge pull request #15464 from tgxworld/improve_notifications_logic

Improvements to ActiveSupport::Notifications.
Merge pull request #15379 from xuanxu/rational_precision

Fix AS::NumberHelper results with rationals
just use `assert`
File.exist? instead of File.exists? in bin/setup

File.exists? is deprecated in Ruby 2.1+

https://github.com/ruby/ruby/blob/v2_1_2/file.c#L1413
Add missing colon to internal
Remove unused `initialize_attributes` method

This was previously a hook for a special case related to `serialize`,
which has since been removed.
Merge pull request #15473 from sgrif/sg-missing-colon

Add missing colon to internal [ci skip]
Merge pull request #15474 from unixmonkey/master

File.exist? instead of File.exists? in bin/setup