Discourage use of jupyter notebooks in python sections

[SashaWeinstein]

My assumption is that people who are only comfortable with jupyter notebooks but not .py files come from a data analyst background where the code they write doesn't need to be readable by others. Generally speaking people who can put their code in a .py file are more ready for an engineering role.
For this reason we should put a suggestion in the top of the python section that we prefer .py files that can be run from the command line, or at least a submission where most logic is in functions that are run from a jupyter notebook.