'Label' in twitter_bootstrap_twitter_bootstrap_btn_dropdown should inherit formats

If you want to make a split dropdown, you can use twitter_bootstrap_twitter_bootstrap_btn_dropdown. The label though should automatically inherit the button styling. This would be nicer than passing the class on ourselves.

function twitter_bootstrap_twitter_bootstrap_btn_dropdown($variables) {

  ...

  // Ad as string if its not a link
  if(is_array($variables['label'])) {
	  $variables['label']['attributes']['class'][] = 'btn';
	  $variables['label']['attributes']['class'][] = 'btn-'. $variables['type'];
	  $output .= l($variables['label']['title'], $variables['label']['href'], $variables['label']);
  }