+ attribution: document.location.protocol === 'https:' ?
+ "Tiles courtesy of <a href='http://www.mapquest.com/' target='_blank'>MapQuest</a> <img src='https://developer.mapquest.com/content/osm/mq_logo.png'>" :
+ "Tiles courtesy of <a href='http://www.mapquest.com/' target='_blank'>MapQuest</a> <img src='http://developer.mapquest.com/content/osm/mq_logo.png'>"