moving know_object out of the base class

object is only common to constant and object slots (which should be unified)
On the way to making the array recursive

lib/slot_machine/slot.rb

@@ -29,17 +29,16 @@ module SlotMachine
       end
     end
 
-    attr_reader :known_object , :slots
+    attr_reader :slots
     # is an array of symbols, that specifies the first the object, and then the Slot.
     # The first element is either a known type name (Capitalized symbol of the class name) ,
     # or the symbol :message
     # And subsequent symbols must be instance variables on the previous type.
     # Examples:  [:message , :receiver] or [:Space , :next_message]
-    def initialize( object , slots)
+    def initialize( slots)
       raise "No slots #{object}" unless slots
       slots = [slots] unless slots.is_a?(Array)
-      @known_object , @slots = object , slots
-      raise "Not known #{slots}" unless object
+      @slots =  slots
     end
 
     def to_s