code: function getChangesSince() {
              var opts = $.extend({heartbeat : 10 * 1000}, options, {
                feed : "longpoll",
                since : since
              });
              ajax(
                {url: db.uri + "_changes"+encodeOptions(opts)},
                options,
                "Error connecting to "+db.uri+"/_changes."
              );
            }
docs: actually make the changes request