add installation instructions to pkg packages

pkg/serialization/lib/serialization.dart

 // Copyright (c) 2012, 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.
 
 /**
  * This provides a general-purpose serialization facility for Dart objects. A
  * [Serialization] is defined in terms of [SerializationRule]s and supports
  * reading and writing to different formats.
  *
+ * ## Installing ##
+ *
+ * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
+ * file.
+ *
+ *     dependencies:
+ *       serialization: any
+ *
+ * And then run `pub install`.
+ *
  * Setup
  * =====
  * A simple example of usage is
  *
  *      var address = new Address();
  *      address.street = 'N 34th';
  *      address.city = 'Seattle';
  *      var serialization = new Serialization()
  *          ..addRuleFor(address);
  *      Map output = serialization.write(address);
@@ skipping 154 matching lines @@
  * take a [ClassMirror] in their constructor, and we cannot serialize those. So
  * when we read the rules, we must provide a Map<String, Object> which maps from
  * the simple name of classes we are interested in to a [ClassMirror]. This can
  * be provided either in the [namedObjects] variable of the Serialization,
  * or as an additional parameter to the reading and writing methods on the
  * [Reader] or [Writer] respectively.
  *
  *     new Serialization()
  *       ..addRuleFor(new Person(), constructorFields: ["name"])
  *       ..namedObjects['Person'] = reflect(new Person()).type;
+ *
+ * [pub]: http://pub.dartlang.org
  */
 library serialization;
 
 import 'src/mirrors_helpers.dart';
 import 'src/serialization_helpers.dart';
 import 'dart:async';
 import 'dart:json' as json;
 import 'dart:collection';
 
 part 'src/reader_writer.dart';
@@ skipping 275 matching lines @@
 }
 
 /**
  * An exception class for errors during serialization.
  */
 class SerializationException implements Exception {
   final String message;
   const SerializationException([this.message]);
   toString() => "SerializationException($message)";
 }