fix a lot of Tkinter imports
diff --git a/Demo/tkinter/matt/canvas-gridding.py b/Demo/tkinter/matt/canvas-gridding.py
index 84f4ea0..2f9d23a 100644
--- a/Demo/tkinter/matt/canvas-gridding.py
+++ b/Demo/tkinter/matt/canvas-gridding.py
@@ -1,4 +1,4 @@
-from Tkinter import *
+from tkinter import *
 
 # this is the same as simple-demo-1.py, but uses
 # subclassing.