code: function(key) {
      var bits = key.split('.');
      var value = item;
      for (var i = 0; i < bits.length; i++) {
        value = value[bits[i]];
        if (!value) return '';
      }
      if (!value) return '';
      if (typeof value === 'function') value = value();
      if (typeof value === 'number' && value < 10) {
        return '0' + value;
      }
      return value;
    }
docs: generate the destination of a post via permalink style