code: function composite ( comb, zero ) {
          return function ( conf, value, fieldMeta ) {
              var validators = conf.value;
              return reduce(function ( acc, v ) {
                  var f = VALIDATORS[ v.rule ];
                  checkRuleExistence( f, v.rule );
                  return comb( acc, f( v, value, fieldMeta ) );
              }, zero, validators ); 
          };
      }
docs: Build composite validator, which
  combines result of all nested validators
  by `comb` function.
  
  @param {Function} comp - `and`, `or`, etc.
  @param {Object} zero - intital value of composite
  validator result.
  @returns {Function)