Update navigation example after Navigator changes

Now this example uses the App widget to drive the adventure game.

examples/widgets/navigation.dart

@@ -2,31 +2,27 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:sky/material.dart';
 import 'package:sky/src/fn3.dart';
 
-List<Route> routes = [
-  new Route(
-    name: 'home',
-    builder: (navigator, route) => new Container(
+final Map<String, RouteBuilder> routes = <String, RouteBuilder>{
+  '/': (NavigatorState navigator, Route route) => new Container(
     padding: const EdgeDims.all(30.0),
     decoration: new BoxDecoration(backgroundColor: const Color(0xFFCCCCCC)),
     child: new Column([
       new Text("You are at home"),
       new RaisedButton(
         child: new Text('GO SHOPPING'),
-          onPressed: () => navigator.pushNamed('shopping')
+        onPressed: () => navigator.pushNamed('/shopping')
       ),
       new RaisedButton(
         child: new Text('START ADVENTURE'),
-          onPressed: () => navigator.pushNamed('adventure')
+        onPressed: () => navigator.pushNamed('/adventure')
       )],
       justifyContent: FlexJustifyContent.center
     )
-    )
   ),
-  new Route(
-    name: 'shopping',
-    builder: (navigator, route) => new Container(
+  '/shopping': (NavigatorState navigator, Route route) => new Container(
     padding: const EdgeDims.all(20.0),
     decoration: new BoxDecoration(backgroundColor: const Color(0xFFBF5FFF)),
     child: new Column([
@@ -37,15 +33,12 @@ List<Route> routes = [
       ),
       new RaisedButton(
         child: new Text('GO TO DUNGEON'),
-          onPressed: () => navigator.push(routes[2])
+        onPressed: () => navigator.pushNamed('/adventure')
       )],
       justifyContent: FlexJustifyContent.center
     )
-    )
   ),
-  new Route(
-    name: 'adventure',
-    builder: (navigator, route) => new Container(
+  '/adventure': (NavigatorState navigator, Route route) => new Container(
     padding: const EdgeDims.all(20.0),
     decoration: new BoxDecoration(backgroundColor: const Color(0xFFDC143C)),
     child: new Column([
@@ -57,32 +50,17 @@ List<Route> routes = [
       justifyContent: FlexJustifyContent.center
     )
   )
-  )
-];
-
-class NavigationExampleApp extends StatefulComponent {
-  NavigationExampleAppState createState() => new NavigationExampleAppState();
-}
-
-class NavigationExampleAppState extends State<NavigationExampleApp> {
-  NavigatorHistory _history = new NavigatorHistory(routes);
+};
 
-  void onBack() {
-    if (_history.hasPrevious()) {
-      setState(() {
-        _history.pop();
-      });
-    } else {
-      // TODO(abarth): Integrate with the system navigator.
-      // super.onBack();
-    }
-  }
-
-  Widget build(BuildContext context) {
-    return new Row([new Navigator(_history)]);
-  }
-}
+final ThemeData theme = new ThemeData(
+  brightness: ThemeBrightness.light,
+  primarySwatch: Colors.purple
+);
 
 void main() {
-  runApp(new NavigationExampleApp());
+  runApp(new App(
+    title: 'Navigation Example',
+    theme: theme,
+    routes: routes
+  ));
 }