make all instances attr read writers

unfortunately the writers have to have self.var =
otherwise it is just a local var
Also need to make the type explicit for all
Protocol included memory_length on the class for now

lib/parfait/block.rb

@@ -16,7 +16,7 @@ module Parfait
     end
 
     def inspect
-      "#{@self_type.object_class.name}(#{arguments_type.inspect})"
+      "#{self_type.object_class.name}(#{arguments_type.inspect})"
     end
   end
 end