update readme

README.md

 这是一个vue+element+axios+webpack2的管理后台 先占个坑
-效果预览
+效果预览
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+###两步验证登录 支持微信和qq
+![两步验证 here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/2login.gif)
+
+####真正的动态换肤
+![真正的动态换肤](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/theme.gif)
+
+####可收起侧边栏
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/leftmenu.gif)
+
+####拖拽排序
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/order.gif)
+
+####上传裁剪头像
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/uploadAvatar.gif)
+
+#####富文本(整合七牛 打水印等个性化功能)
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/editor.gif)
+
+####封装table组件
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/table.gif)
+
+#### 图表
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/echarts.gif)
+
+####导出excel
+![enter image description here](https://github.com/PanJiaChen/vue-element-admin/blob/master/gifs/excel.png)
+
+等等很多，尽请期待！