补充完善了拓展组件的说明

Author: jaweii

README.MD

@@ -72,5 +72,5 @@ li标签包裹的元素，就是显示在组件列表视图的元素，其中li
 
  [4]: https://raw.githubusercontent.com/jaweii/Vue-Layout/master/docs/images/App%20Bar1.png
  [5]: https://raw.githubusercontent.com/jaweii/Vue-Layout/master/docs/images/Header%201.png
- [5]: https://raw.githubusercontent.com/jaweii/Vue-Layout/master/docs/images/getTemplate.png
+ [6]: https://raw.githubusercontent.com/jaweii/Vue-Layout/master/docs/images/getTemplate.png