*Rails 3.1.0 (unreleased)*

* No changes

*Rails 3.0.2 (unreleased)*

* No changes

*Rails 3.0.1 (October 15, 2010)*

* No Changes, just a version bump.

*Rails 3.0.0 (August 29, 2010)*

* Added ActiveModel::MassAssignmentSecurity [Eric Chapweske, Josh Kalderimis]

* JSON supports a custom root option: to_json(:root => 'custom')  #4515 [Jatinder Singh]

* #new_record? and #destroyed? were removed from ActiveModel::Lint. Use
  persisted? instead. A model is persisted if it's not a new_record? and it was
  not destroyed? [MG]

* Added validations reflection in ActiveModel::Validations [JV]

    Model.validators
    Model.validators_on(:field)

* #to_key was added to ActiveModel::Lint so we can generate DOM IDs for
  AMo objects with composite keys [MG]

* ActiveModel::Observer#add_observer!

  It has a custom hook to define after_find that should really be in a
  ActiveRecord::Observer subclass:

    def add_observer!(klass)
      klass.add_observer(self)
      klass.class_eval 'def after_find() end' unless klass.respond_to?(:after_find)
    end

* Change the ActiveModel::Base.include_root_in_json default to true for Rails 3 [DHH]

* Add validates_format_of :without => /regexp/ option. #430 [Elliot Winkler, Peer Allan]

  Example :

      validates_format_of :subdomain, :without => /www|admin|mail/

* Introduce validates_with to encapsulate attribute validations in a class.  #2630 [Jeff Dean]

* Extracted from Active Record and Active Resource.