remus workers are now able to be seamless terminated.

Previously when the worker was told to terminate by the server it would
shutdown all messages between the worker and server. Instead now it stops
taking messages from the server, but still acts like it can send messages.
This allows the worker to 'finish' its current task before finding out
it needs to shutdown.
Merge pull request #193 from robertmaynard/seamless_worker_termination

Seamless worker termination