Add Auto dismiss for .alert

Created by: vin-ai

It would be nice if .alert element keeps a property of auto dismiss time out. So, that .alert item will disappear in given time without writing extra code for dismiss or get user input.

<div class="alert">
    <button type="button" class="close" data-dismiss="alert">&times;</button>
    <strong>Warning!</strong> Best check your self, you're not looking too good.
</div>

Should be customizable by jQ plugin or just by adding an extra attribute to button element. Like

...
<button type="button" class="close" data-dismiss="alert" data-auto-dismiss="5">&times;</button>
...

Above attribute value for data-auto-dismiss could be in sec or what ever more appropriate than sec.