add Sketch, Shape, Line, Circle placeholder classes

Circle.py

@@ -0,0 +1,3 @@
+
+class Circle(Shape):
+    pass

Line.py

@@ -0,0 +1,3 @@
+
+class Line(Shape):
+    pass

Shape.py

@@ -0,0 +1,3 @@
+
+class Shape(object):
+    pass

Sketch.py

@@ -0,0 +1,10 @@
+
+class Sketch(object):
+    def __init__(self):
+        self.shapes = []
+
+    def __iter__(self):
+        return self.shapes.__iter__()
+
+    def __contains__(self, item):
+        return self.shapes.__contains__(item)

Window.py

@@ -4,6 +4,8 @@ import gtk.gtkgl
 
 from OpenGL.GL import *
 
+from Sketch import Sketch
+
 class Window:
     def __init__(self, title):
         self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)