Improved explanation of what's here

Demo/tkinter/README

-The subdirectory "guido" contains my original example set.
-A more interesting and coherent collection is in the subdirectory "matt".
+Several collections of example code for Tkinter.
+
+See the toplevel README for an explanation of the difference between
+Tkinter and tkinter, how to enable the Python Tk interface, and where
+to get Matt Conway's lifesaver document.
+
+Subdirectories:
+
+guido		my original example set (fairly random collection)
+matt		Matt Conway's examples, to go with his lifesaver document
+www		a progressing sequence of www clients using Tk
+howard		some dialogs contributed by Ken Howard