Jobs that timeout will never be able to run again

When a job overruns it's TTR, beanstalkd will increment the job's timeout stat and put it back on the work queue for another worker to reserve.

In an effort to prevent pathological jobs from dog-piling all available workers, `cmdstalk` [will bury a task it reserves that has timeouts greater than 1](https://github.com/99designs/cmdstalk/blob/master/broker/broker.go#L112). This means that once a task is buried because of a timeout, it will _always_ re-bury instantly each time it is kicked: the job becomes un-runnable.

Using just the `buried`, `kicked` and `timeout` counters, there does not appear to be a way to differentiate between "kicks due buries due to timeouts" in the way that would allow `cmdstalk` to bury a job the next time it is reserved after a timeout.

The `beanstalkd` protocol docs make mention of [a one second grace period](https://github.com/kr/beanstalkd/blob/master/doc/protocol.txt#L224) at the end of a reserve time - would it be possible to use this grace period to bury a timed out job in the "same run" as the timeout occurred?

The issue is in broker/broker.go line 112 where jobs with timeouts > 1 are buried. Examine the beanstalkd protocol's grace period mentioned in the docs to see if a job can be buried within the same run after a timeout. Look at how the timeout counter is tracked and when the bury decision is made. Test changes by running jobs that exceed TTR and checking if they become permanently buried.

索引モデルが issue の本文から書いたものです。