(Suggestion) Refactor the refactor lesson

I think the refactor lesson could be broken up into more discrete sections. I think this order might be best.

- break into functions (true refactor)
- `if __name__=="__main__": main() `
- importing
- documentation

While it is probably best practice to write doc strings immediately when writing a function, but forces us to spend a lot of time typing with the learners instead of getting to new material. I think that making them less formal will help with this. We can always display what a proper set of docstrings looks like using a fully fledged Python package like numpy or pandas.