clarify/improve imports & import discussion

public/docs/dart/latest/guide/displaying-data.jade

@@ -18,7 +18,6 @@
 
   code-tabs
     code-pane(language="dart" name="web/main.dart" format="linenums").
-      import 'package:angular2/angular2.dart';
       import 'package:angular2/bootstrap.dart';
       import 'package:displaying_data/show_properties.dart';
 
@@ -50,9 +49,14 @@
           entry_points: web/main.dart
   p.
    All of this code should look familiar from the previous page,
-   except for the import of <code>show_properties.dart</code>
-   in <code>main.dart</code>.
-   That import statement lets you implement part of the app in a different Dart file.
+   except for the imports in <code>main.dart</code>.
+   The import of <code>show_properties.dart</code>
+   lets you implement part of the app in a different Dart file.
+   You've previously seen <code>angular2.dart</code> imported,
+   but that's unnecessary here because this version of <code>main.dart</code>
+   doesn't implement any components or other injectable types.
+
+  p.
    All three of these files remain similar in the rest of the examples,
    so we'll focus on what changes.
 
@@ -325,7 +329,6 @@
         List&lt;String&gt; names = ['Aarav', 'Martín', 'Shannon', 'Ariana', 'Kai'];
       }
     code-pane(language="dart" name="web/main.dart" format="linenums").
-      import 'package:angular2/angular2.dart';
       import 'package:angular2/bootstrap.dart';
       import 'package:displaying_data/show_properties.dart';
 
@@ -430,26 +433,33 @@
 
     p.
       The app's entry point—<code>main.dart</code>—imports
-      <code>angular2.dart</code> and <code>bootstrap.dart</code>.
+      <code>bootstrap.dart</code> so that it can call <code>bootstrap()</code>.
       Both <code>show_properties.dart</code> and <code>friends_service.dart</code>
-      import only <code>angular2.dart</code>
-      because they aren't entry points.
+      import <code>angular2.dart</code>
+      so that they can define Angular components and models.
 
     code-example(language="dart").
       // In web/main.dart:
-      import 'package:angular2/angular2.dart';
       import 'package:angular2/bootstrap.dart';
       ...
+      bootstrap(...)
+      ...
 
       // In lib/show_properties.dart:
       ...
       import 'package:angular2/angular2.dart';
       ...
+      @Component(...)
+      @View(...)
+      ...
 
       // In lib/friends_service.dart:
       ...
       import 'package:angular2/angular2.dart';
       ...
+      @Injectable()
+      ...
+
 
     p.
       For more information on implementing Dart libraries, see

public/docs/dart/latest/guide/user-input.jade

@@ -167,7 +167,6 @@
         }
       }
     code-pane(language="dart" name="web/main.dart" format="linenums").
-      import 'package:angular2/angular2.dart';
       import 'package:angular2/bootstrap.dart';
       import 'package:user_input/todo_list.dart';