specify TTL on removeOnComplete

To keep track of successful jobs (their payloads), it could be useful to keep the job alive for a predetermined time.

This can be accomplished very easily specifying a TTL in the REDIS hash containing job informations.

The API could be:

```
queue.create( ... ).removeOnComplete( 3600 * 24 ).save()
```

In such way the job informations would be available for 24 hours prior to automatic removal by REDIS
Do you think it's a valid use-case?

No files or tests are named. Start by locating the queue.create(...).removeOnComplete implementation and the Redis hash lifecycle; determine how a TTL could be passed through the API. Done means successful job data remains available for the requested duration and is then removed automatically, with coverage for the new behavior.

Written by the indexing model from the issue text.