Commits for Review

[bonnfire]

Updated commits on 7/12:
Intro to Data (with flights) : 6f25925
---- Question about arrange(desc()) not working with mean() %>%, legend titles

Multiple Regression: 37acacd
---- In response to your comments, do you mind reading this version? How does the prediction calculation sound? Also, investigated GGally:ggcatsmat() for changing the point size (I agree, the "points" don't seem point-like), doesn't seem like it's as customizable as it is convenient. I played around with another GGally function ggpairs(), which seemed to have the size argument, but I didn't try too hard there. Let me know your thoughts.

I have included a screenshot of the LaTeX when knitted into HTML on my laptop, doesn't seem to be a problem, so I don't know why this is a recurring problem when we read your printed versions.

@nicholasjhorton