static removeClass(element, className){
        if( StickySidebar.hasClass(element, className) ){
          if (element.classList)
            element.classList.remove(className);
          else
            element.className = element.className.replace(new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi'), ' ');
        }
      }
Remove specific class name to specific element
@static
@param {ObjectDOM} element 
@param {String} className