Alert hide instead of remove

This allows the alert to be reused.

For instance, I have the following HTML already on the page prior to any events taking place.

```html
<div class="alert-box success hide" data-alert>
  <strong>The email has been sent</strong>
</div>
```
This gets shown whenever the user clicks the export button on a page. If they want to export it multiple times, but happen to have closed the alert between each export, they won't get the alert because currently closing the alert performs a ```remove()```.