add installation instructions to pkg packages

pkg/intl/lib/intl.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 library provides internationalization and localization. This includes
  * message formatting and replacement, date and number formatting and parsing,
  * and utilities for working with Bidirectional text.
  *
+ * ## Installing ##
+ *
+ * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
+ * file.
+ *
+ *     dependencies:
+ *       intl: any
+ *
+ * And then run `pub install`.
+ *
  * For things that require locale or other data, there are multiple different
  * ways of making that data available, which may require importing different
  * libraries. See the class comments for more details.
  *
  * There is also a simple example application that can be found in the
  * `example/basic` directory.
+ *
+ * [pub]: http://pub.dartlang.org
  */
 library intl;
 
 import 'dart:async';
 import 'src/intl_helpers.dart';
 import 'dart:math';
 import 'date_symbols.dart';
 import 'src/date_format_internal.dart';
 import "number_symbols.dart";
 import "number_symbols_data.dart";
@@ skipping 247 matching lines @@
    * unless for some reason this gets called inside a message that resets the
    * locale.
    */
   static String getCurrentLocale() {
     if (_defaultLocale == null) _defaultLocale = systemLocale;
     return _defaultLocale;
   }
 
   toString() => "Intl($locale)";
 }