update list of changes, fix a link

Generated from the XML (see https://github.com/dart-lang/dart-up-and-running-book/commit/94c88adaeb3ef0a10efd11b32e0aa61febabe2ac for XML diffs).

The link change fixes the problem that would've been fixed by
https://github.com/dart-lang/dartlang.org/pull/354.

Review URL: https://chromiumcodereview.appspot.com/460083002