Allow tests to proceed as soon as the payload changes, instead of always having to wait for a timeout

[#6455 state:committed]
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

Mismatches between migrations and constants have nothing to do with
pluralization rules or model names. The mismatch happens between
the camelization of the filename minus timestamp, and the name of
the migration class itself.

This reverts commit 1c21f75f.

Signed-off-by: NXavier Noria <fxn@hashref.com>

Remove test which was broken on 1.8. This test is now irrelevant since singular associations no longer return a proxy object.

Conflicts:
	activerecord/lib/active_record/associations/association.rb
	activerecord/lib/active_record/fixtures.rb

Added a bullet point there showing how the Uninitialized Constant
(missing migration class) error looks like.

Split AssociationProxy into an Association class (and subclasses) which manages the association, and a CollectionProxy class which is *only* a proxy. Singular associations no longer have a proxy. See CHANGELOG for more.

Allow building and then later saving has_many :through records, such that the join record is automatically saved too. This requires the :inverse_of option to be set on the source association in the join model. See the CHANGELOG for details. [#4329 state:resolved]

Ensure that association_ids uses the correct attribute where the association is a has_many :through with a :primary_key option on the source reflection. [#6376 state:resolved]

[#6442 state:committed]
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>