added threading and ability for client request to specify processing time
added threading and ability for client request to specify processing time

pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io,pauldardeau/python-concurrent-disk-io