Have all intermediate Python notebooks use same data files

Do to changes made after the introductory notebook was created, a
change in filename structure and contents was needed to keep the
lessons simple. This updates the intro lecture to use the same
files as the following lessons.
Rerun intro intermediate Python notebook using new files
Remove old intermediate Python data files
Merge pull request #497 from ethanwhite/inter-py-filenames

Have all intermediate Python use the same data files