Add support for scheduled Faktory jobs#2

## Overview Adds the ability to schedule jobs. In the example below I included a standard (non-scheduled) job to show no regression in existing functionality. Example usage: ```php $client = new FaktoryClient('faktory', '7419'); $job1 = new FaktoryJob('CoolJob1', [ 1, 2 ]); $job2 = new FaktoryJob('CoolJob2', [ 3, 4 ]); $job3 = new FaktoryJob('CoolJob3', [ 5, 6 ]); $job4 = new FaktoryJob('CoolJob4', [ 7, 8 ]); $job5 = new FaktoryJob('CoolJob5', [ 9, 10 ]); $job1->inSeconds(300); $job2->inMinutes(15); $job3->inHours(24); $date = date(DATE_RFC3339, strtotime('+5 days')); $job4->at($date); $client->push($job1); $client->push($job2); $client->push($job3); $client->push($job4); $client->push($job5); ``` Faktory Dashboard from the above code: