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 # => false

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

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

Jeff Dean