Add appveyor badge to README.

Author: N. Taylor Mullen

README.md

@@ -1,5 +1,7 @@
 Razor Tooling
 =====
+AppVeyor: [![AppVeyor](https://ci.appveyor.com/api/projects/status/ks1xkw9q65ha47ip/branch/dev?svg=true)](https://ci.appveyor.com/project/aspnetci/razortooling/branch/dev)
+
 Travis:   [![Travis](https://travis-ci.org/aspnet/RazorTooling.svg?branch=dev)](https://travis-ci.org/aspnet/RazorTooling)
 
 The Razor syntax provide a fast, terse, clean and lightweight way to combine server code with HTML to create dynamic web content. This repo contains tooling that interacts with the DNX Design Time Host to provide a Razor editing experience.