WIP: ability to kick failed jobs back onto queue.

Background: https://github.com/99designs/cmdstalk/issues/2

TL;DR: kicking failed jobs causes them to be instantly re-buried based on their stats.

This change means each `kick` buys a job one more `release` or `timeout` before it's auto-buried.

/cc @lwc.

---

For reference, here's a sample `stats-job` output:

```yaml
---
id: 3
tube: cmdstalk-test-465396aa983f063a
state: buried
pri: 10
age: 34
delay: 0
ttr: 1
time-left: 0
file: 0
reserves: 2
timeouts: 1
releases: 0
buries: 1
kicks: 0
```
Ah sorry, should have paid more attention to subject line.