currentPage page's item dom no active

```
<input type="number" v-model="currentPage"/>
<b-pagination class="col-sm-12" align="center" size="sm" :total-rows="total" v-model="currentPage" :per-page="10"></b-pagination>
```

change input's value , b-pagination component is change ,but no active css effect.


![image](https://user-images.githubusercontent.com/8503065/43692843-4381ef88-995d-11e8-83af-ebb3cff49652.png)
