Incorrect Alert markup

The `Alert` class is not producing the correct markup when closeable: it's placing the closing anchor after the message, while it should be placed before it. It matters because, as the element has `position:relative`, it ends up in the wrong location.

For instance, `Alert::error('My message')` should be producing
```html
<div class="alert-error alert">
	<a href="#" class="close" data-dismiss="alert">&times;</a>
	My message
</div>
```
but, instead, produces
```html
<div class="alert-error alert">
	My message
	<a href="#" class="close" data-dismiss="alert">&times;</a>
</div>
````

This is how the alert looks like with the incorrect markup:
![image](https://f.cloud.github.com/assets/2119933/515915/43f840ac-be8e-11e2-9299-8af0cdbb348a.png)