Explaining code formatting and including more links

[k8hertweck]

Pointed to this repo by @jgolob , and want to offer the following recommendations based on my experience teaching folks new to Python:

• explain what code comments are and why they are used here (e.g., why is some text in markdown cells and other text in commented lines?)
• How and why do you split code onto separate lines (in the same cell)? This partially relates to your existing explanation of whitespace, and also relates to code that functions vs style issues.
• I'm a huge fan of links to other resources. Off the top of my head, I'd include:
  • overview of Jupyter notebooks (shortcuts, how to use it, etc)
  • documentation for packages used (pandas, seaborn, etc)

Of course, these suggestions aren't essential for the material to work beautifully; I'm really glad to have this as an example for this type of analysis!