Ignore a method if exception raised when trying to serialize it.
Use semaphores and deques to synchronize access to message queues.

This method avoids using sleep()s which slow down the system by
delaying message handling even when there are available messages.
The system is now more "event-based" and so doesn't require sleeping.
The receive() method also doesn't need to return None anymore when
the inbound_queue is empty.
Refactor a lot of the Message-related code into Message class from Messenger.
Style fix.
Style fix.
Style fix.
Style fix.
Style fix.
Style fix.
Add tests for schedule.py and update README.md.
Add a section for jobs.
Version v0.0.3