python-package to tell if the pdf needs ocr to detect the text.

This is a minimal python package, 

Contributing:

Please do! Guidelines:

 - This lesson is for beginners. Yes there are plenty of super fancy things we don't cover here; someday, we'll make a different, super fancy lesson to teach those things.
 - Max 100 lines per PR please.
 - Open an issue or empty PR first to talk about controversial changes.
