Suggested Edits for @tegacodes's Data Vis Chapter

@tegacodes, I went through and made a few grammar/word choice edits directly.  Other comments are noted with **[mh: notes notes notes]**, but the github markdown doesn't play nice with the html formatting you are using.

I realize your chapter isn't done yet, so you might be planning on doing this anyway...but my biggest suggestion at the moment would be to give the reader the layout of your chapter somewhere early on.  They should know exactly what they will learn and in what order.  Specifically I'd want to know: what datasets we going to be visualizing, where to get them, what we are going to be trying to visualize about those datasets, what parts of the process are going to happen in openFrameworks and what parts of the process are going to happen outside of openFrameworks.  (And I'd want to know those things either in section 1 or in the first part of section 2.)

There's a lot of great information in the chapter.  It just comes across as a little bit jumbled without first giving the reader a mental roadmap of the path you are going to be taking them on.

Hope this helps!