Add a new Theme widget to control color and text color of apps

sky/examples/widgets/styled_text.dart

Index: sky/examples/widgets/styled_text.dart
diff --git a/sky/examples/widgets/styled_text.dart b/sky/examples/widgets/styled_text.dart
index 4ce79bd63a6c115c4bed8d2d80bf71030960445e..6ca309fe4a19896b49c5668a4d5669cb29c1354b 100644
--- a/sky/examples/widgets/styled_text.dart
+++ b/sky/examples/widgets/styled_text.dart
@@ -7,10 +7,12 @@ import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/rendering/sky_binding.dart';
 import 'package:sky/theme/colors.dart';
+import 'package:sky/theme/theme_data.dart';
 import 'package:sky/theme/typography.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/material.dart';
 import 'package:sky/widgets/scaffold.dart';
+import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/tool_bar.dart';
 import 'package:sky/widgets/widget.dart';
 
@@ -105,11 +107,13 @@ HAL: This mission is too important for me to allow you to jeopardize it.''';
       onPointerDown: toggleToTextFunction
     );
 
-    return new Scaffold(
-      body: new Material(child: interactiveBody),
-      toolbar: new ToolBar(
-        center: new Text('Hal and Dave', style: white.title),
-        backgroundColor: Blue[500]
+    return new Theme(
+      data: new ThemeData(color: Blue, text: white),
+      child: new Scaffold(
+        body: new Material(child: interactiveBody),
+        toolbar: new ToolBar(
+          center: new Text('Hal and Dave', style: white.title)
+        )
       )
     );
   }