[bug] fix issue #22

better multi-process logging management: this was not strictly necessary when running the process pool with fork, because the forked processes would inherit the default logging configuration from the parent process

nevertheless, this could have been problematic as well--if multiple processes were all logging to stdout (the default) it could have become garbled (I have just never seen it happen, under low load)

this ensures that all logs from the process pool are handled with a QueueHandler, and a thread is spawned to manage the queue and pass log messages from the process pool to the main process's logger