This reverts commit 9d396ee8, reversing
changes made to fa2bfd83.

Reason: the change broke the build.

Add a proxy_association method to association proxies, which can be called by association extensions to access information about the association. This replaces proxy_owner etc with proxy_association.owner.

This reverts commit 04cc446d.

I reverted it because apparently we want to use: select([:a, :b])
instead of select(:a, :b), but there was no tests for that form.

Simplify the test by using id and name. `id` will be the only real sort criteria in any case as it's unique.

American English(according to Weber)

fix behavior when after_initialize is defined and a block is passed to Base.create

Children attributes can be either String's or Symbol's, so let's check if the object responds to to_i.

The previous behavior was unintentional, and some people was relying on it. Now the dynamic finder will always expecting the number of arguments to be equal or greater (so you can still pass the options to it.)

So if you were doing this and expecting the second argument to be nil:

    User.find_by_username_and_group("sikachu")

You'll now get `ArgumentError: wrong number of arguments (1 for 2).` You'll then have to do this:

    User.find_by_username_and_group("sikachu", nil)

One duplicate was eliminated: test_to_xml_including_methods/
test_methods_are_called_on_object.

Cache key was incorrectly using timezone-dependent record#updated_at when it should be using a timezone-independent value to generate the cache key

Minor refactoring to cache_key timezone test

Closes #2059

Adds a test to validate the format of the cache_key for nil and present updated_at values

Correctly handles updated_at == nil

having raises NoMethodError: undefined method `empty?' when a Fixnum or Date/Time were passed via varargs