review FrontMatter.Rnw for Teaching Statistics using R

[nicholasjhorton]

There was a considerable amount of reference to instructors as the primary audience in the CommonMaterial/FrontMatter.Rnw. I made this more generic, which probably necessitates adding a section to StartTeaching with discussion of audience. Several parts commented out include:

%Nevertheless, those who are unfamiliar with \R\ or who have never used \R\ for teaching are understandably cautious about using it with students. If you are in that category, then this book is for you. Our goal is to reveal some of what we have learned teaching with \R\ and to make teaching statistics with \R\ as rewarding and easy as possible -- for both students and faculty. We will cover both technical aspects of \R\ and \RStudio\ (e.g., how do I get \R\ to do thus and such?) as well as some perspectives on how to use computation to teach statistics. The latter will be illustrated in \R\ but would be equally applicable with other statistical software.

%Others have used \R\ in their courses, but have perhaps left the course feeling
like there must have been better ways to do this or that topic. If that
sounds more like you, then this book is for you, too. As we have been working
on this book, we have also been developing the \pkg{mosaic}