Suggested edits and comments

-- are comments I've made, I don't intend for you to merge them directly.

Overall this was pretty good. The main issue I have was with warnings showing up in the REPL sessions, the foldr jazz session was just confusing, and after that section I got confused about whether we were in a REPL context of file context for some of the code snippets.

I'd try to make this stick tighter to our goal of building a csv parsing application, and ground a few of the more unusual concepts in why we're using them (this is pretty minor, I think you did really well for the most part). Also we never uploaded to Hackage.