Fixes skipping object callback filters

This allows you to skip callbacks that are defined by objects, e.g. for
`ActionController`:

    skip_after_filter MySpecialFilter

Previously this didn't work due to a bug in how Rails compared callbacks
in `Callback#matches?`. When a callback is compiled, if it's an object
filter (i.e. not a method, proc, etc.), `Callback` now defines a method on
`@klass` that is derived from the class name rather than `@callback_id`.
So, when `skip_callback` tries to find the appropriate callback to
remove, `Callback` can regenerate the method name for the filter
object and return the correct value for `Callback#matches?`.
Fix loading of string arrays in postgres
options_from_collection_for_select helper takes html attributes

as the last element of the array
Fix freeze applying to cloned objects

Previously, freezing a cloned ActiveRecord object froze the original
too. By cloning `@attributes` before freezing, we prevent cloned objects
(which in Ruby share state of ivars) from being effected by `#freeze`.

Resolves issue #4936, which has further information on this issue, as
well as steps to reproduce.

* Add a test case for `#freeze` not causing `cloned.frozen?` to be true.
* Clone @attributes before freezing in `ActiveRecord::Core`, then
  reassign the cloned, frozen hash to the frozen model's `@attributes`
  ivar.

/cc @steveklabnik
Use db:test:load instead of db:test:load_schema

db:test:load task should be favored over db:test:load_schema, because it
checks for chosen format (ActiveRecord::Base.schema_format).

closes #10227
Fixed typos in AR CHANGELOG
Merge pull request #10228 from prathamesh-sonpatki/AR-Typos

Fixed typos in AR CHANGELOG
Fix documentation to the custom Deprecator

[ci skip]
The third argument of deprecation_warning is always optional

[ci skip]
replace match with get verb in ActionController::Metal
Merge pull request #10230 from gaurish/remove-match

replace match with get verb in ActionController::Metal
converts the project README to Markdown

We tend to use Markdown for everything but the API, the
README is no longer used as the home page of the API
after 7a5aa72, so we can now migrate it.
editorial touch, remove these dots
Extract a base class from ActiveSupport::LogSubscriber

Adds a ActiveSupport::Subscriber base class that LogSubscriber inherits
from. By inheriting from Subscriber, other kinds of subscribers can take
advantage of the event attachment system.
Merge pull request #10218 from dasch/dasch/extract-subscriber-class

Extract a Subscriber base class from LogSubscriber
Copy-edits in the ActiveSupport::Subscriber documentation.

Thank you @fxn :green_heart::yellow_heart::heart::purple_heart::blue_heart:

[ci skip]
Ruby On Rails -> Ruby on Rails [ci skip]
Fix #7619. 0x prefix must be added when assigning hexadecimal string into bit column in Postgresql, because solving ambiguity.
Merge pull request #8206 from kennyj/fix_7619-2

Fix #7619. 0x prefix must be added when assigning hexadecimal string into bit column in Postgresql, because solving ambiguity.
fixes gemspec