Changes to be merged when 0.9.11 goes out

Changes to the tutorial and demos for 0.9.11. Tutorial source code changes are in a separate repo.

The test/ directory was a convenient way for me to test the demos (it isn't pushed to the site), but it isn't strictly necessary.

Note: The backend demo test doesn't work right now. Once you manipulate enough pubspec.yamls to get packages to download, Dart Editor doesn't like the routing code...