code: function crawLink($,result,linkTag, callback) {
        var link = $(linkTag).attr('href');
        var parentUrl = result.url;
  
        if (link) {
  
            var rel =  $(linkTag).attr('rel');
  
            if (result.linkTypes.indexOf(rel) > 0) {
                var linkUri = URI.linkToURI(parentUrl, link);
  
                pm.crawlLink(parentUrl, linkUri, null, null, function(){
                  addLinkToQueue(result, parentUrl, linkUri, null, null, callback);
                });
            }
            else {
              callback();
            }
        }
        else {
          callback();
        }
  }
docs: Extract info of html link tag & send the info to the plugins
  
  
  @param The HTML body containing the link (Cheerio wraper)
  @param The http response with the crawl options
  @param The link tag
  @param callback()