Allow different defaults

[george-carlin]

E.g. allow for this kind of setup in an initializer file:

OrderOrder.config do |c|
  c.default_name_column = "title"
  c.default_time_column = "date"
end

Now User.alphabetical will sort by title, not name, negating to need to pass "title" as an argument.

Maybe even allow setting this at the model level? E.g.

class User < ActiveRecord::Base
  self.alphabetical_column = "name"
  self.chronological_column = "date"
end