code: function updateDepth(parentUrl, linkUri, callback) {
  
      var depths = {parentUrl : parentUrl, linkUri : linkUri, parentDepth : 0, linkDepth : 0};
      var execFns = async.seq(getDepths , calcultateDepths , saveDepths);
  
      execFns(depths, function (error, result) {
        if (error) {
           return callback(error);
        }
        callback(error, result.linkDepth);
      });
  
  }
docs: Compute the crawl depth for a link in function of the crawl depth
  of the page that contains the link
  
  @param The URI of page that contains the link
  @param The link for which the crawl depth has to be calculated
  @param callback(error, depth)