text: /**
   * Serializes an object to a query string; ensures each key is not null.
   * @memberOf serialize
   * @category serialize
   * @param {Object} obj Required.
   * @returns {String} String.
   */
  module.exports = function (obj) {
    var str = [];
    if (!obj) {
      return '';
    }
    for (var p in obj)    {
      if (obj.hasOwnProperty(p) && obj[p] !== null) {
        str.push(encodeURIComponent(p) + '=' + encodeURIComponent(obj[p]));
      }
    }
    return str.join('&');
  };
  