Added hash methods for both Action and State, and fixed their __str__ methods.
Introduced the SuccessorFunction and added a test case for continuously adding mappings in the Successor Function.  I haven't yet added a good way to test the multi-valued nature of the SuccessorFunction, but the print outs check out.
Fixed a bug within SuccessorFunction: states should not be able to be mapped to (action, resulting_state) pairs that have the same action but that have different resulting states.
Adding skeleton search problem fields.
Made Action and State inherit from object.
Added method for returning the Set of applicable Actions in a given State.
Added skeleton for method to resolve an Action in a given State, which will return the State that results.