code: function(rule, message) {
        if (is_object(rule)) {
          _messages = extend({}, _messages, rule);
        } else if (is_string(rule)) {
          _messages[rule] = message;
        }
      }
docs: add custom messages
  
  @param {String/Object} rule
  @param {String}        message
  
  @return {Void}