Add chapter intros

[pjcozzi]

Let's add the intros for each chapter (and perhaps a representative figure - that would be awesome), to the table of contents page under the brief contents. We could also link to the code for that chapter from that (#4) and perhaps even link to the author bios on the contributor's page.

[pjcozzi]

@gnlnx please hold off on this for a day or two. I'm still trying to figure out the details, and will do the first few chapters as an example before you start.

[gnlnx]

Sounds good.

I'm playing around with a slightly different style to show the TOC that I will check in in the next day or so. I will continue to keep the current version up to date as well and I'll open up an issue so you can review the other TOC when I check it in. I can't promise it will be better but just wanted to try something since this is such an important and info heavy page.

[pjcozzi]

Duplicate with #11.