Introduce boot.js: this finally makes it possible to load and run Todomvc

example/todomvc/web/app.dart

Index: example/todomvc/web/app.dart
diff --git a/example/todomvc/web/app.dart b/example/todomvc/web/app.dart
index 15aacf7b7dee87676b87bef04a64dad0e5b4585d..c2cbe85c62b3b0be951b48ed8675d81bc8fb13f8 100644
--- a/example/todomvc/web/app.dart
+++ b/example/todomvc/web/app.dart
@@ -5,10 +5,10 @@
 library app;
 
 import 'dart:html';
-import 'package:observe/observe.dart';
 import 'package:polymer/polymer.dart';
 import 'model.dart';
 
+@CustomTag("todo-app")
 class TodoApp extends PolymerElement with ObservableMixin {
   @observable AppModel app;
   bool get applyAuthorStyles => true;