update book and book generation script for pre-M3

In another CL (or CLs), I'll update the rest of the site. We also need to update samples; I'll look into that.

Staged at:

http://api.dart-lang.appspot.com/docs/dart-up-and-running/

Changes are summarized at:

http://api.dart-lang.appspot.com/docs/dart-up-and-running/contents/preface.html#preface-updates

Review URL: https://chromiumcodereview.appspot.com/12049077