add installation instructions to pkg packages

pkg/meta/lib/meta.dart

Index: pkg/meta/lib/meta.dart
diff --git a/pkg/meta/lib/meta.dart b/pkg/meta/lib/meta.dart
index ba49c2b63db136d7eff9e71a8ce2d39473d87fb0..285f25408f12c482fc34f4a3f884238889c4c8ca 100644
--- a/pkg/meta/lib/meta.dart
+++ b/pkg/meta/lib/meta.dart
@@ -6,6 +6,18 @@
  * This library contains the definitions of annotations that provide additional
  * semantic information about the program being annotated. These annotations are
  * intended to be used by tools to provide a better user experience.
+ *
+ * ## Installing ##
+ *
+ * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
+ * file.
+ *
+ *     dependencies:
+ *       meta: any
+ *
+ * And then run `pub install`.
+ *
+ * [pub]: http://pub.dartlang.org
  */
 library meta;