About Refactor

Plan to put the settings in the `AtCtrl`.

```
<form ng-controller="AtCtrl">

    <textarea at-user 
              at-auto-complete
              ng-model="message.content"
              ng-trim="false"></textarea>

    <ul at-user-list>
        <li ng-click="autoComplete(object)">
            <img />
            <span>{{ user.name }}</span>
        </li>
    </ul>  

</form>
```
