Contracts for accepting and returning types

Runtime checker of types of input and output
@accepts decorator to ensure types of parameters
@returns decorator to ensure type of return value
Backend for Advance Wars clone

Units exist on a World, made of Tiles.
Units have an armor type, a list of attacks,
and a movement type.
Units can attack each other and communication with
this backend process can be done with tcp network calls.
Adding Makefile for automated testing
Adding main. Simply listens on 127.0.0.1:8080