rename the XX_slot classes to SlottedXX

move to slotted and slots (wip)

lib/slot_machine/slot.rb

@@ -19,11 +19,11 @@ module SlotMachine
     def self.for(object , slots)
       case object
       when :message
-        MessageSlot.new(slots)
+        SlottedMessage.new(slots)
       when Constant
-        ConstantSlot.new(object , slots)
+        SlottedConstant.new(object , slots)
       when Parfait::Object , Risc::Label
-        ObjectSlot.new(object , slots)
+        SlottedObject.new(object , slots)
       else
         raise "not supported type #{object}"
       end