[WIP] update for AngularDart 1.x

@kwalrath could you please review when you are available.

/ref https://github.com/angular/angular.dart.tutorial/pull/131
Is it important to leave out the mixin and subclass?

Also, saying "as well" implies that it might be used in addition to the expando, rather than instead of. 

Perhaps return to the old phrasing. (Also, note that the paragraph is missing its final period.)