use "object" baseclass for unspecified superclasses

SketchWidget.py

@@ -10,7 +10,7 @@ from shapes import *
 from constraints import *
 from Sketch import *
 
-class SketchWidget:
+class SketchWidget(object):
     def __init__(self, sketch, window):
         self.sketch = sketch
         self.window = window

Window.py

@@ -5,7 +5,7 @@ from Sketch import Sketch
 from SampleSketch import SampleSketch
 from SketchWidget import SketchWidget
 
-class Window:
+class Window(object):
     def __init__(self, title):
         self.mode_buttons_to_names = {}
         self.mode_names_to_buttons = {}