Add span classes to label element in div case

Could you please add a span class field to the label_element in the DIV fieldgroup instance.

This will enable you to add stuff like font icons or css icons to the field group (fieldset) title.

someting like:

$output .= '<h2><span $element_attributes['class']>' . $title . '</span></h2>';

can become 

<h2><span class="glyphicon glyphicon-search">Search</span></h2>

I home it makes sence

Thanks, this is a great module