Alias attribute and the dirty methods (_changed? etc)

Rails currently doesn't support the dirty methods for an attribute
alias's.

i.e. if you setup an alias called title
(alias_attribute :title, :name) then title_changed? isn't defined.

Rich has written a simple patch so the dirty methods are defined for
attribute alias's -> http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/812

Please +1 it if you'd find it useful.

Thanks Rich

Tim.