Added raw create contacts/entities methods.

I'd like to add these methods to keep a consistent way of communicating with the flapjack api via a client library. Right now, I'm using a CLI tool to communicate with flapjack, and if possible, I want to avoid going outside of the flapjack-diner library for any calls to flapjack. In order for my tool to work as intended, I need to be able to create contacts and entities via flapjack-diner.