### 基本用法
```html
<u-loading></u-loading>
```

### 大小扩展

``` html
<u-linear-layout direction="vertical">
    <div><u-loading size="small"></u-loading> small </div>
    <div><u-loading></u-loading> normal </div>
    <div><u-loading size="large"></u-loading> large </div>
</u-linear-layout>
```
