Add query attributes to associations

I just added a patch to lighthouse that adds query attribute methods
to associations. This makes associations behave more like any other
attribute -

class Post < ActiveRecord::Base
  has_many :comments
end

Post.new.comments? # => false

It adds query attribute methods to has_one (and through), has_many
(and through), belongs_to (works with polymorphic) and
has_and_belongs_to_many.

If that looks interesting / worthwhile, you can plus one it at:

http://rails.lighthouseapp.com/projects/8994/tickets/311-patch-add-query-attribute-methods-to-associations

Jeff Dean