has_normalized_sti
==================

This extension will allow Rails STI to work a normalized type column.

For example

  create_table :people, :force => true do |t|
    t.string  :full_name
    t.integer :type_id
  end

  create_table :person_types, :force => true do |t|
    t.string :type_name
  end

  class Person < ActiveRecord::Base
    has_normalized_sti
  end

  class PersonType < ActiveRecord::Base
  end

  after calling has_normalized_sti:
  * type - returns the name of the class of the type just as regular STI
  * type= - set the type to something specific like regular STI
  * normal_type - the Type object through the relation


Configuration options are:
  * type_class_name - belong_to this model for the type storage
    (default: #{class_name}Type)
  * foreign_key - specifies the column for id of the type (default: type_id)
  * type_column - specifies the column name for the type string on the types table
    (default: type_name)

Override example

  create_table :people, :force => true do |t|
    t.string  :full_name
    t.integer :special_type_id
  end

  create_table :person_types, :force => true do |t|
    t.string :special_person_type
  end

  class SpecialPerson < ActiveRecord::Base
    set_table_name :people
    has_normalized_sti :type_class_name => 'SpecialPersonType', :type_column => 'special_person_type', :foreign_key => 'special_type_id'
  end

  class SpecialPersonType < ActiveRecord::Base
    set_table_name :person_types
  end