move setting initial_state codes to StateMachine class

lib/aasm/base.rb

@@ -31,7 +31,6 @@ module AASM
     # define a state
     def state(name, options={})
       @state_machine.add_state(name, @klass, options)
-      @state_machine.initial_state = name if options[:initial] || !@state_machine.initial_state
 
       @klass.send(:define_method, "#{name.to_s}?") do
         aasm.current_state == name

lib/aasm/state_machine.rb

@@ -28,8 +28,15 @@ module AASM
     end
 
     def add_state(name, klass, options)
+      set_initial_state(name, options)
       @states << AASM::State.new(name, klass, options) unless @states.include?(name)
     end
 
+    private
+
+    def set_initial_state(name, options)
+      @initial_state = name if options[:initial] || !initial_state
+    end
+
   end # StateMachine
 end # AASM