[Bug Report]不能兼容IE10 及以下版本

### Environment
WIndows10/IE10/iview-admin v2.0-beta.2

### Reproduction link
[https://admin.iviewui.com/home](https://admin.iviewui.com/home)

### Steps to reproduce
把IE 浏览器调制10 以下
Make Internet explorer 10 or less

### What is expected?
兼容IE8 以上版本
Compatible with IE8 and above

### What is actually happening?
空白页面
A blank page

Start with the reproduction link in the reported Windows 10/IE10 environment and follow the listed steps using IE10 or below. Compare the blank page with the expected behavior, then identify the browser-compatibility failure from the project entry point. Done means the admin page renders rather than showing a blank page in IE8 and above.

Written by the indexing model from the issue text.