Use bootstrap-alert close event instead of jQuery.remove()

In order for bootstrap-alert events to fire on delayed close we need to
use the alert event 'close' instead.

Example:
```javascript
    $.bootstrapGrowl('X', {delay: 0}).bind('close', function() { // No delay close event
      $.bootstrapGrowl('Y').bind('close', function() { // Delay close with close event
        $.bootstrapGrowl('Z');
      });
    });
```