add delay jobs

[yanqibin]

https://yanqibin.github.io/2018/02/22/php-resque%E5%BB%B6%E8%BF%9F%E6%89%A7%E8%A1%8C%E4%B8%8E%E5%A4%B1%E8%B4%A5%E9%87%8D%E8%AF%95/

[danhunsaker]

Duplicates resque/php-resque#4

Would love to see this as a PR over there, though!