add installation instructions to pkg packages

pkg/yaml/lib/yaml.dart

Index: pkg/yaml/lib/yaml.dart
diff --git a/pkg/yaml/lib/yaml.dart b/pkg/yaml/lib/yaml.dart
index 94e3d4220f48c4ad3b0dff931a8029d116420770..86fca23b5e897c69d708c684787b35631bf36ed7 100644
--- a/pkg/yaml/lib/yaml.dart
+++ b/pkg/yaml/lib/yaml.dart
@@ -4,6 +4,18 @@
 
 /// A parser for [YAML](http://www.yaml.org/).
 ///
+/// ## Installing ##
+///
+/// Use [pub][] to install this package. Add the following to your `pubspec.yaml`

[Andrei Mouravski, 2013/04/19 20:13:35]

Line too long.

[sethladd, 2013/04/19 20:32:43]

Done.

+/// file.
+///
+///     dependencies:
+///       yaml: any
+///
+/// And then run `pub install`.
+///
+/// ## Using ##
+///
 /// Use [loadYaml] to load a single document, or [loadYamlStream] to load a
 /// stream of documents. For example:
 ///
@@ -22,6 +34,8 @@
 ///       var doc = loadYaml("YAML: YAML Ain't Markup Language");
 ///       print(json.stringify(doc));
 ///     }
+///
+/// [pub]: http://pub.dartlang.org
 library yaml;
 
 import 'src/composer.dart';