docs(dart): update sample code to be more uniform, use b2

closes #766

public/docs/_examples/forms/dart/lib/hero.dart

@@ -1,6 +1,4 @@
 // #docregion all
-library hero_form.hero;
-
 class Hero {
   int number;
   String name;

public/docs/_examples/forms/dart/lib/hero_form_component.dart

@@ -1,10 +1,9 @@
 // #docplaster
 // #docregion
 // #docregion no-todo
-library hero_form.hero_form_component;
-
 import 'package:angular2/angular2.dart';
-import 'package:hero_form/hero.dart';
+
+import 'hero.dart';
 
 const List<String> _powers = const [
   'Really Smart',

public/docs/_examples/forms/dart/lib/hero_form_component_initial.dart

@@ -1,6 +1,4 @@
 // #docregion
-library hero_form.hero_form_component;
-
 import 'package:angular2/angular2.dart';
 
 @Component(selector: 'hero-form', template: 'Hero form will go here')

public/docs/_examples/forms/dart/pubspec.yaml

@@ -2,13 +2,16 @@
 name: hero_form
 description: Form example
 version: 0.0.1
+environment:
+  sdk: '>=1.13.0 <2.0.0'
 dependencies:
-  angular2: 2.0.0-beta.0
+  angular2: 2.0.0-beta.2
   browser: ^0.10.0
+  dart_to_js_script_rewriter: ^0.1.0
 transformers:
 - angular2:
     platform_directives:
     - 'package:angular2/common.dart#CORE_DIRECTIVES'
     - 'package:angular2/common.dart#FORM_DIRECTIVES'
     entry_points: web/main.dart
-
+- dart_to_js_script_rewriter