Job on complete event

When fetching a job like this -

```
kue.Job.get(someId, (err, job) => {
job.on('complete', () => { // never called
debug('on get')
// do stuff after job is complete
})
job.inactive()
})
```

here this event handler is never called, probably because `kue.Job.get` doesn't return an object that has that listener. **Is there a way to listen to job events when fetching events like this ?
or a way to listen to `complete` event for a particular job (by job id)**

This works fine, but doesn't serve the purpose -

```
const job = queue.create('name', {
title
})
.delay(1200000)
.attempts(3)
.save(err => {
if(err)
return
// save job.id
})
job.on('complete', () => {
debug('on create')
})
```

Start with the kue.Job.get and queue.create entry points, then compare how the fetched job and newly created job handle job.on('complete') and inactive(). Reproduce the example with a saved job id and verify whether completion for that particular job can be observed; done means the documented fetch-by-id flow reliably triggers or exposes the requested completion event.

Written by the indexing model from the issue text.