Remove Widgets Demo, it's broken and doesn't provide any value over Stocks App

R=ianh@google.com, ojan@chromium.org

Review URL: https://codereview.chromium.org/1085933002

examples/widgets/main.sky

-#!mojo mojo:sky_viewer
-<!--
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
--->
-<sky>
-<import src="/sky/framework/debug/shake-to-reload.sky" />
-<script>
-import 'widgets_app.dart';
-void main() {
-  new WidgetsApp();
-}
-</script>
-</sky>

examples/widgets/widgets_app.dart

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:sky/framework/fn.dart';
-import 'package:sky/framework/components/button.dart';
-import 'package:sky/framework/components/input.dart';
-import 'package:sky/framework/components/popup_menu.dart';
-
-class WidgetsApp extends App {
-  static final Style _menuStyle = new Style('''
-    position: absolute;
-    top: 200px;
-    left: 200px;''');
-
-  PopupMenuController controller;
-
-  UINode build() {
-    return new Container(
-      children: [
-        new Button(key: 'Go', content: new Text('Go'), level: 1),
-        new Button(key: 'Back', content: new Text('Back'), level: 3),
-        new Input()
-
-        // PopupMenu requires a PopupMenuController and should be wired up
-        // to a button to create the controller only when the menu is open, etc.
-        // new Container(
-        //   style: _menuStyle,
-        //   children: [
-        //     new PopupMenu(
-        //       controller: controller,
-        //       items: [
-        //         [new Text('People & options')],
-        //         [new Text('New group conversation')],
-        //         [new Text('Turn history off')],
-        //         [new Text('Archive')],
-        //         [new Text('Delete')],
-        //         [new Text('Un-merge SMS')],
-        //         [new Text('Help & feeback')],
-        //       ],
-        //       level: 4),
-        //     ]
-        //   )
-        // ]
-      );
-  }
-}