Review/test The Basics

[zstumgoren]

Review, update and test the following (in Codespaces), as needed:

• basics/README.md
• basics/basics_reference_notebook.ipynb
• completed/basics_reference_completed.ipynb
• basics/basics_notebook.ipynb
• completed/basics_complete_notebook.ipynb

[zstumgoren]

@esagara @tommeagher the basics/README.md contains the following text (towards bottom):

**The files**

* `basics.py and complete/basics_complete.py

You know off-hand if these are typos that should refer to the Notebook files instead?

Or perhaps this section of the README is defunct? Wondering if everything from `The files`` down was an earlier, pre-notebook iteration. And if so, can we delete all this to tighten up the README and direct folks to the relevant notebooks for this section?