fix a lot of Tkinter imports
diff --git a/Demo/tkinter/guido/ss1.py b/Demo/tkinter/guido/ss1.py
index d957907..6a7aefc 100644
--- a/Demo/tkinter/guido/ss1.py
+++ b/Demo/tkinter/guido/ss1.py
@@ -485,7 +485,7 @@
         s = chr(m+ord('A')) + s
     return s
 
-import Tkinter as Tk
+import tkinter as Tk
 
 class SheetGUI: