Documentation improvements/corrections.

We're always looking for ways to improve documentation, specifically in the README for this repo.

This may include corrections to typos, fact checks, prose clarification, additional sections/topics to help users, etc.

NOTE: While we are certainly open to corrections to inline comments, we subscribe to the idea that code should be self-documenting. In other words, if comments are needed, it is either because the code needs to be written better (broken down into smaller modules, or named better, e.g.), or because there is a "why" or some additional context warranted. Comments should not be added to break up the code or say what the code does. The code breaks itself up and says precisely what it does already.