add installation instructions to pkg packages

pkg/oauth2/lib/oauth2.dart

Index: pkg/oauth2/lib/oauth2.dart
diff --git a/pkg/oauth2/lib/oauth2.dart b/pkg/oauth2/lib/oauth2.dart
index 7fdb205557a5e45879a76308e79e3d5f54f6f4ec..f68fd73539d8000d80b571e47b90e9c0ad04dd1b 100644
--- a/pkg/oauth2/lib/oauth2.dart
+++ b/pkg/oauth2/lib/oauth2.dart
@@ -6,6 +6,16 @@
 /// behalf of a user, and making authorized HTTP requests with the user's OAuth2
 /// credentials.
 ///
+/// ## 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:
+///       oauth2: any
+///
+/// And then run `pub install`.
+///
 /// OAuth2 allows a client (the program using this library) to access and
 /// manipulate a resource that's owned by a resource owner (the end user) and
 /// lives on a remote server. The client directs the resource owner to an
@@ -100,6 +110,8 @@
 ///         }).then((file) => file.close()).then((_) => result);
 ///       });
 ///     }).then(print);
+///
+/// [pub]: http://pub.dartlang.org
 library oauth2;
 
 export 'src/authorization_code_grant.dart';