Tweetable or Quotable Wordpress Shortcode

// [quotable]"Here's my quote."[/quotable]
// [quotable link="" class="" link_class=""]"Here's my quote."[/quotable]
// if link says 'no', use only content, no permalink
//=========================================================== TWEET THIS SHORTCODE
function quotable_shortcode( $atts, $content = null ) {
	extract(shortcode_atts(array(
		'class' => 'no_lede',
		'link' => '',
		'link_class' => '',
	), $atts));

	$return_string = '';
	if(isset($content)) {
    	$content = strip_tags($content);
        if (empty($link)) $link = get_permalink();
		$return_string = "<blockquote class='$class quotable'><p class='$class'>$content<br />
            <a target='_blank' class='twitter icon_btn $link_class' 
                href='https://twitter.com/intent/tweet?text=$content&url=$link&via=fizzle' 
                title='Click to share on Twitter!'><span>Tweet This</span>
            </a></p></blockquote>";        
	}
	return $return_string;

}
add_shortcode('quotable', 'quotable_shortcode');