code: function(additionalRules, opts) {
    if (check(additionalRules).is('undefined')) {
      return true;
    }
  
    if (check(additionalRules).is.not('object')) {
      logger.warn('Provide an mapping of custom rules');
      return false;
    }
  
    _.each(additionalRules, function(rule, ruleName) {
      if (check(rule).is.not('function') || check(ruleName).is.not('string')) {
        logger.warn('Invalid custom rule provided');
        return;
      }
  
      rules[ruleName] = rule;
      opts[ruleName] = opts[ruleName] || true;
    });
  
    return true;
  }
docs: /*
  addRules
  
  Add custom rules to the rule list and enable in the rule options hash.