Updated link to VS extension.

readme.md

@@ -27,7 +27,7 @@ using Direct2D and other operating systems using Gtk & Cairo.
 
 Perspex is now in alpha. What does "alpha mean? Well, it means that it's now at a stage where you
 can have a play and hopefully create simple applications. There's now a [Visual
-Studio Extension](https://visualstudiogallery.msdn.microsoft.com/87db356c-cec9-4a07-b7db-a4ed8a921ac9)
+Studio Extension](https://visualstudiogallery.msdn.microsoft.com/a4542e8a-b56c-4295-8df1-7e220178b873)
 containing project and item templates that will help you get started, and
 there's an initial complement of controls. There's still a lot missing, and you
 *will* find bugs, and the API *will* change, but this represents the first time