simplify ActiveSupport.test_order definition

It was not done to be included

Use directly TZInfo::Timezone without proxy

This was used by the respond_to/respond_with implementation on this
file, which is now extracted to the responders gem.

This functionality has been extracted to the responders gem.

bebugger doesn't work with Ruby 2.2 so we don't need to support it
anymore

Now that we only support Ruby 2.2+ we don't need this conditional
anymore

Now that Rails requires Ruby >= 2.0 there is need to skip the
`test_depend_on_path` test.

The hack so skip a Thread test for Ruby 1.9 can be removed now that
Rails requires Ruby >= 2.0.

Conflicts:
	activerecord/test/cases/transactions_test.rb

A special `if` statement to support `Psych` for Ruby < 2.0 can be
dropped now that Rails requires Ruby >= 2.0.

Now that Rails requires Ruby >= 2.0, there is no need to check whether
`BigDecimal` exists or not.

Conflicts:
	activerecord/lib/active_record/attribute_methods/read.rb

Add has_secure_token to Active Record

Since real timezone is loaded anyway in `#utc_offset`
which is called during `#create`

Update SecureToken Docs

Add Changelog entry for has_secure_token [ci skip]

Remove unneeded `require 'as/deprecation'`

Tests should still pass after removing `require 'active_support/deprecation'`
from these files since the related deprecations have been removed.

Add missing information regarding callbacks

Remove all deprecation code

These requires were added only to change deprecation message

Before this change we had a small set of "truthy", and all others
are "falsy".

Now, we have a small set of "falsy" values and all others are
"truthy" matching Ruby's semantics.

Before this change any error raised inside a transaction callback
are rescued and printed in the logs.

Now these errors are not rescue anymore and just bubble up,
as the other callbacks.