Update charted to 0.4.8 and roll

packages/usage/lib/usage_io.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/**
- * In order to use this library import the `usage_io.dart` file and
- * instantiate the [AnalyticsIO] class.
- *
- * You'll need to provide a Google Analytics tracking ID, the application name,
- * and the application version.
- */
+/// In order to use this library import the `usage_io.dart` file and
+/// instantiate the [AnalyticsIO] class.
+///
+/// You'll need to provide a Google Analytics tracking ID, the application name,
+/// and the application version.
 library usage_io;
 
-import 'src/usage_impl.dart';
-import 'src/usage_impl_io.dart';
-
+export 'src/usage_impl_io.dart' show AnalyticsIO;
 export 'usage.dart';
-
-/**
- * An interface to a Google Analytics session, suitable for use in command-line
- * applications.
- */
-class AnalyticsIO extends AnalyticsImpl {
-  AnalyticsIO(String trackingId, String applicationName, String applicationVersion) :
-    super(
-      trackingId,
-      new IOPersistentProperties(applicationName),
-      new IOPostHandler(),
-      applicationName: applicationName,
-      applicationVersion: applicationVersion);
-}