code: function stringifyObject(obj, prefix) {
    var ret = []
      , keys = objectKeys(obj)
      , key;
    for (var i = 0, len = keys.length; i < len; ++i) {
      key = keys[i];
      ret.push(stringify(obj[key], prefix
        ? prefix + '[' + encodeURIComponent(key) + ']'
        : encodeURIComponent(key)));
    }
    return ret.join('&');
  }
docs: Stringify the given `obj`.
  
  @param {Object} obj
  @param {String} prefix
  @return {String}
  @api private