Version 1.3 release.

Updates CHANGELOG, version, docs.
diff --git a/CHANGELOG b/CHANGELOG
index 7892645..fc3275d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,12 @@
+v1.3
+  Version 1.3
+
+  Add support for the Google Application Default Credentials.
+  Require python 2.6 as a minimum version.
+  Update several API samples.
+  Finish splitting out oauth2client repo and update tests.
+  Various doc cleanup and bugfixes.
+	
 v1.2
   Version 1.2