Restructured README.md

[lalalainexd]

The lack of specificity and organization of the README was a bit confusing so I tried to reorganizing it to be more like a set-by-step instructional manual.

[geeksam]

Thanks, Elaine, for the reminder to look at this. We have an internal version of this repo, which is what those of us who do remote pairing at LS actually use. This is a sanitized public version, which unfortunately means that it has to be kept in sync manually. I've added a note to the internal version of the README to help remind people to keep this one up to date as well.

A few months ago, I had done a significant revamp of the README in our internal version, but apparently I forgot to apply those changes over here. I've done that, but in the process I may have lost track of some of the changes you made. (Unfortunately, the diff format makes it hard to tell the difference between simply moving lines around and actual content changes.) If you have time, I'd appreciate your feedback on the changes. (Of course, given that you're in gSchool, I'll totally understand if you don't have the time!)

And again: thanks!