Add a queue full() API

[brendan-simon-indt]

I notice there is a queue empty() API but not a queue full() API. Standard python queues have both, so thought it made sense to provide the same for persistent queues.

   def full(self):
        return self.qsize() == self.maxsize

I want to remove an item from the front of the queue if it is full before pushing a new item to the back of the queue - and do something with the old item that was removed. Basically, I'm using the queue is a FIFO of fixed size and what old items to pop off the end.

The put() API doesn't have a return value (e.g. a popped off item from a full queue), but that's consistent with queue.Queue, so I can't do an atomic put and get (if full). That's why the full() API would be handy (not that it's hard to explicitly test the queue size (pq.qsize() == pq.maxsize)

So would you consider adding the full() API or a PR to complement the empty() API and make it consistent with queue.Queue?

[peter-wangxu]

Looks like full() api is available since python3.x but not exist in python2.x
I am fine to add this api.
Do you mind sending a new PR for this?

[brendan-simon-indt]

Done. See PR #194