Project: foxes-and-rabbits-v2   
Authors: Michael Kölling and David J. Barnes   
   
This project is part of the material for chapter 10 of the book   

   Objects First with Java - A Practical Introduction using BlueJ
   Seventh edition
   David J. Barnes and Michael Kölling

A predator-prey simulation involving foxes and rabbits in
an enclosed rectangular field.

This is the second version of the simulation. This version
makes use of inheritance for the animals.

How to start:
    Create a Simulator object.
    Then call one of:
        + simulateOneStep - for a single step.
        + simulate - and supply a number (say 10) for that many steps.
        + runLongSimulation - for a simulation of 700 steps.