fix a lot of Tkinter imports
diff --git a/Demo/tkinter/matt/animation-w-velocity-ctrl.py b/Demo/tkinter/matt/animation-w-velocity-ctrl.py
index 68eb1d0..88309ca 100644
--- a/Demo/tkinter/matt/animation-w-velocity-ctrl.py
+++ b/Demo/tkinter/matt/animation-w-velocity-ctrl.py
@@ -1,4 +1,4 @@
-from Tkinter import *
+from tkinter import *
 
 # this is the same as simple-demo-1.py, but uses
 # subclassing.