[Bug Report] 被popup包裹的range组件无法实现与v-model双向绑定

### VUX version
2.9.2

### OS/Browsers version
Win10 x64

### Vue version
2.5.17

### Code

```html

import {Range, Group, Popup, Cell} from 'vux'

export default {
name: 'Senior',
components: {Range, Group, Popup, Cell},
data () {
return {
show: true,
light: 50
}
}
}

```

### Steps to reproduce
代码为组件完整代码 复制粘贴即可重现

### What is Expected?
确认是否为bug

### What is actually happening?
去掉popup即可正确显示