Memory leak about pgn2data

[RegisGraptin]

It seems that it is a concurrency issues.
When you create the worker, the limit is set to 0, indicating an infinite size. In process.py

q = queue.Queue(maxsize=0)
worker = Thread(target=self.__process_move_queue, args=(q,))

I think this is the cause of the issus I have. So, it might be interesting to add a maximum value as default, to be sure that the elements in the queue are processed.

[zq99]

Thanks for investigating and highlighting this issue.

The latest version (v.0.0.9) has queue size as an optional parameter in the export method:

`from converter.pgn_data import PGNData

filename = 'caruana_carlsen_2018.pgn'
pgn_data = PGNData(filename)
result = pgn_data.export(queue_size=1000)
`

This makes it easier to fit in the testing framework. Hopefully, this gives enough flexibility to overcome this memory issue.