`configure_dependency` actually defined callbacks, so rename the method
and move it to the appropriate method.

This reverts commit 1468a4b8.

order on the old ones

The previous behavior added a major backward incompatibility since it
impossible to have a upgrade path without major changes on the
application code.

We are taking the most conservative path to be consistent with the idea
of having a smoother upgrade on Rails 4.

We are reverting the behavior for what was in Rails 3.x and,
if needed, we will implement a new API to prepend the order clauses in
Rails 4.1.

This adds the ability for rails apps or gems to have granular control
over how a domain object is converted to sql. One simple use case would
be to add support for Regexp. Another simple case would be something
like the following:

    class DateRange < Struct.new(:start, :end)
      def include?(date)
        (start..end).cover?(date)
      end
    end

    class DateRangePredicate
      def call(attribute, range)
        attribute.in(range.start..range.end)
      end
    end

    ActiveRecord::PredicateBuilder.register_handler(DateRange,
      DateRangePredicate.new)

More complex cases might include taking a currency object and converting
it from EUR to USD before performing the query.

By moving the existing handlers to this format, we were also able to
nicely refactor a rather nasty method in PredicateBuilder.

* Constantize parse token
* Remove extra param passed to `parse_data`

The select_all method always returns ActiveRecord::Result instance,
and the ActiveRecord::Result includes Enumerable mixin.
If #empty?, #first method returns nil. Thus we can simplify this method.

Move model mutation to the methods that are called on the model.