Function groupByIteratee

mocha_test/groupBy.js:8–13

(callOrder, val, next)

    this.timeout(250);

    function groupByIteratee(callOrder, val, next) {
        setTimeout(function() {
            callOrder.push(val);
            next(null, val+1);
        }, val * 25);
    }

    context('groupBy', function() {
        it('basics', function(done) {