rename meta to singleton class

seems more appropriate, as it is the class for a single object
Also seems to be called that on the net (don't remember where the meta came from, but it's gone)

lib/parfait/class.rb

@@ -17,7 +17,7 @@
 module Parfait
   class Class < Behaviour
 
-    attr_reader :name , :super_class_name , :meta_class
+    attr_reader :name , :super_class_name , :singleton_class
 
     def self.type_length
       6
@@ -30,7 +30,7 @@ module Parfait
       super(instance_type)
       @name = name
       @super_class_name = superclass
-      @meta_class = MetaClass.new( self , self.type || @name)
+      @singleton_class = SingletonClass.new( self , self.type || @name)
     end
 
     def rxf_reference_name