adding exceptions for QueueMe

[vsoch]

This will add an exceptions module to replace many of the sys.exits in the library. We maintain sys.exit when we are interacting with the client, however, as exit is the correct action to take.

• This will close #34

Signed-off-by: vsoch vsochat@stanford.edu

[vsoch]

@yarikoptic I think I addressed all your concerns so I'm going to merge! Open an issue when you get some time to review again if there are remaining issues.