function promo_block($atts, $content = null) {
extract(shortcode_atts(array(
"img" => '',
"description" => '',
"title" => ''
), $atts));
return '<div class="col-md-4 promo-block">
            <img src="'.get_template_directory_uri().'/img/svg/'.$img.'.svg" height="64" alt="">
            <h3>'.$title.'</h3>
            <p>'.$description.'</p>
          </div>';
}
add_shortcode("pb", "promo_block");