add installation instructions to pkg packages

BUG=

Review URL: https://codereview.chromium.org//14188048

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/stack_trace@21770 260f80e4-7a28-3924-810f-c04153c831b5

pkgs/stack_trace/lib/stack_trace.dart

diff --git a/pkgs/stack_trace/lib/stack_trace.dart b/pkgs/stack_trace/lib/stack_trace.dart
index 5747b85..f031f95 100644
--- a/pkgs/stack_trace/lib/stack_trace.dart
+++ b/pkgs/stack_trace/lib/stack_trace.dart
@@ -2,6 +2,23 @@
 // 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.
 
+/**
+ * ## Installing ##
+ *
+ * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
+ * file.
+ *
+ *     dependencies:
+ *       stack_trace: any
+ *
+ * Then run `pub install`.
+ *
+ * For more information, see the
+ * [stack_trace package on pub.dartlang.org][pkg].
+ *
+ * [pub]: http://pub.dartlang.org
+ * [pkg]: http://pub.dartlang.org/packages/stack_trace
+ */
 library stack_trace;
 
 export 'src/trace.dart';