_autoPurge = function() {
        if (purging) {
            return;
        }
        purging = true;

        var i, q;

        for (i in queues) {
            if (queues.hasOwnProperty(i)) {
                q = queues[i];
                if (q.autopurge && q.finished) {
                    _purge(q.tId);
                    delete queues[i];
                }
            }
        }

        purging = false;
    }
Removes processed queues and corresponding nodes
@method _autoPurge
@private