Port Date Picker example to fn3

examples/widgets/container.dart

@@ -2,17 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:sky/widgets.dart';
+import 'package:sky/src/fn3.dart';
 
-class ContainerApp extends App {
-  Widget build() {
+class ContainerApp extends StatelessComponent {
+  Widget build(BuildContext context) {
     return new Column([
         new Container(
           padding: new EdgeDims.all(10.0),
           margin: new EdgeDims.all(10.0),
           decoration: new BoxDecoration(backgroundColor: const Color(0xFFCCCCCC)),
           child: new NetworkImage(
-            src: "https://www.dartlang.org/logos/dart-logo.png",
+            src: "https://raw.githubusercontent.com/dart-lang/logos/master/logos_and_wordmarks/dart-logo.png",
             width: 300.0,
             height: 300.0
           )

examples/widgets/date_picker.dart

@@ -2,27 +2,30 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:sky/widgets.dart';
+import 'package:sky/src/fn3.dart';
 import 'package:sky/material.dart';
 
 void main() => runApp(new DatePickerDemo());
 
-class DatePickerDemo extends App {
+class DatePickerDemo extends StatefulComponent {
+  DatePickerDemoState createState() => new DatePickerDemoState(this);
+}
 
-  DateTime _dateTime;
-
-  void initState() {
+class DatePickerDemoState extends ComponentState<DatePickerDemo> {
+  DatePickerDemoState(DatePickerDemo config) : super(config) {
     DateTime now = new DateTime.now();
     _dateTime = new DateTime(now.year, now.month, now.day);
   }
 
+  DateTime _dateTime;
+
   void _handleDateChanged(DateTime dateTime) {
     setState(() {
       _dateTime = dateTime;
     });
   }
 
-  Widget build() {
+  Widget build(BuildContext context) {
     return new Theme(
       data: new ThemeData(
         brightness: ThemeBrightness.light,