Update classtree.py

linux:~> classtree.py
[(<type 'object'>, ()),
 [(<class 'turtle.TNavigator'>, (<type 'object'>,)),
  (<class 'turtle.TPen'>, (<type 'object'>,)),
  [(<class 'turtle.RawTurtle'>,
    (<class 'turtle.TPen'>, <class 'turtle.TNavigator'>)),
   [(<class 'turtle.Turtle'>, (<class 'turtle.RawTurtle'>,))]]]]

__builtin__.object()
turtle.TNavigator(__builtin__.object)
turtle.TPen(__builtin__.object)
turtle.RawTurtle(turtle.TPen, turtle.TNavigator)
turtle.Turtle(turtle.RawTurtle)