[Bug Report] Cell 的 label 文字默认强制换行，对英文环境不友好

### VUX version
2.9.2

### OS/Browsers version
不限

### Vue version
2.5.17-beta.0

### Code

```html
https://github.com/airyland/vux/blob/v2/src/components/cell/index.vue#L120

.vux-label {
display: inline-block;
word-wrap: break-word;
word-break: break-all;
}
```

### Steps to reproduce
https://github.com/airyland/vux/blob/v2/src/components/cell/index.vue#L120

cell/index.vue 第 120 行 给 `.vux-label` 添加了强制换行的样式，导致在英文环境下单词被非正常断开，严重影响阅读。

### What is Expected?
去掉强制换行代码

### What is actually happening?
实际在英文环境下会强制换行