update back info for itunescn.com

Author: yyx990803

README.md

@@ -20,6 +20,12 @@ Vue.js is an MIT-licensed open source project. Its ongoing development is made p
   <img width="300px" src="https://raw.githubusercontent.com/vuejs/vuejs.org/master/themes/vue/source/images/strikingly.png">
 </a>
 
+and
+
+<a href="http://www.itunescn.com/">
+  <img width="200px" src="http://i.imgur.com/9LE0Scf.png">
+</a>
+
 ## Intro
 
 Vue.js is a library for building interactive web interfaces. It provides data-reactive components with a simple and flexible API. Core features include:

backers.md

@@ -13,7 +13,7 @@ You can join them in supporting  Vue.js development by [pledging on Patreon](htt
 ### $500
 
 <a href="http://www.itunescn.com/">
-  <img width="360px" src="http://www.itunescn.com/images/chaoqichaoluo-logo.png"> Itunescn.com
+  <img width="360px" src="http://i.imgur.com/9LE0Scf.png">
 </a>
 
 ---