[Bug Report] 在 panel 中，如何使用第三方components?

### VUX version
2.2.0

### OS/Browsers version
win8.1 chrome

### Vue version
2.5.2

### Code

```html

import Vue from 'vue'
import _ from 'underscore'
import ICountUp from 'vue-countup-v2'
import { Flexbox, FlexboxItem, Cell, Tabbar, TabbarItem, Panel } from 'vux'

export default {
name: 'Main',

components: {
'i-count-up': ICountUp,
Flexbox,
FlexboxItem,
Cell,
Tabbar,
TabbarItem,
Panel
},
data () {
return {
list11: [{
src: 'http://somedomain.somdomain/x.jpg',
fallbackSrc: 'http://placeholder.qiniudn.com/60x60/3cc51f/ffffff',
title: '标题一',
desc: '<i-count-up :end-val="10000" :decimals="2"></i-count-up>L',
url: '/component/cell'
},
meta: {
source: '来源信息',
date: '时间',
other: '其他信息'
}
}]
}
},
}

```

### Steps to reproduce
想在list11.desc中，能使用第三方的components

### What is Expected?

### What is actually happening?