…atetime.time

 - Job.job_queue is now weakref.proxy reducing the risk of cyclic
   pointers preventing Job object from being deleted.
 - JobQueue._put(): raise if both next_t and job.interval are None
 - Don't put repeating job back to queue if user had disabled it was
   disabled during the time of execution.
 - New method: Job.is_removed() - promising a consistent API (instead of
   access to private member Job._remove)
 - Documentation fixes.