Process SMSSync return code

[abbyad]

as per @mandric

[mandric]

Related ushahidi/SMSSync#11 and just want to note that the goal for this issue is to get more information about the status of a message after it was sent, ideally to know:

1. whether or not the telecom successfully received the message (phone number was valid etc)
2. message was successfully delivered to device

[mandric]

@browndav @abbyad @garethbowen if you get a chance, send me some feedback on this doc https://gist.github.com/mandric/10280606 I put together some details on how this should work.

[ghost]

This is superseded by #709 at this point. I'm going to assume that this issue represents the SMSSync side of the implementation, and move it to ready. We'll consider #709 to be the medic-webapp and medic-transport side.