_statuses uuid should not removed when expired but the status:uuid key-value exists

when i set
```
Resque::Plugins::Status::Hash.expire_in = 60
```
and i create a job get uuid1 and do
```
loop { Resque::Plugins::Status::Hash.set(uuid1,"message") }
```
after 60 second i create another job,in resque-web statuses page i can't find uuid1's info but  status:uuid still exists in redis.
so i think _statuses uuid should not removed when expired but the status:uuid key-value exists.