Added old function back

I added Sally's old function back into the mix. I decided that she might
not want to lose her old functionality.

Reran my notebook to make sure that the changes didn't break anything.
Added DataFrame Comparison Function

Moved my DataFrame comparison function from the notebook into the
sally.py file.

Also, I made a bunch of changes to the notebook to test the new code and
so that I could share it with Sally and Beth.