Update charted to 0.4.8 and roll

packages/yaml/lib/src/yaml_document.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.
 
-library yaml.yaml_document;
-
 import 'dart:collection';
 
 import 'package:source_span/source_span.dart';
 
 import 'yaml_node.dart';
 
 /// A YAML document, complete with metadata.
 class YamlDocument {
   /// The contents of the document.
   final YamlNode contents;
@@ skipping 41 matching lines @@
   /// The handle for use in the document.
   final String handle;
 
   /// The prefix that the handle maps to.
   final String prefix;
 
   TagDirective(this.handle, this.prefix);
 
   String toString() => "%TAG $handle $prefix";
 }