Add CI status to readme

Author: JunTaoLuo

README.md

@@ -1,5 +1,8 @@
 ASP.NET Core Response Caching
 ========
+AppVeyor: [![AppVeyor](https://ci.appveyor.com/api/projects/status/p52yj0kghdyicvwu/branch/dev?svg=true)](https://ci.appveyor.com/project/aspnetci/ResponseCaching/branch/dev)
+
+Travis:   [![Travis](https://travis-ci.org/aspnet/ResponseCaching.svg?branch=dev)](https://travis-ci.org/aspnet/ResponseCaching)
 
 This repo hosts the ASP.NET Core middleware for response caching.