AM::StateMachine autoloads

activemodel/lib/active_model/state_machine.rb

 module ActiveModel
   module StateMachine
+    autoload :Event, 'active_model/state_machine/event'
+    autoload :Machine, 'active_model/state_machine/machine'
+    autoload :State, 'active_model/state_machine/state'
+    autoload :StateTransition, 'active_model/state_machine/state_transition'
+
     class InvalidTransition < Exception
     end