Add minimum R experience to first day

[ethanwhite]

We can't teach R in this class so we need folks to have a basic working knowledge coming in. On the first day (or before via Canvas) we need to communicate our basic needs:

• Variable assignment, using functions, etc
• dplyr basics
• (maybe) ggplot basics

And then direct students who don't have the background, but want to stay in the class to online resources to get the necessary background.