Modification of minimax.hpp

Added in the include guards.
Modification of tests.cpp

Have a simple test case for the tournament class. Have a game of
checkers that plays!
Added new file tournament.hpp

A file for the tournament class.
Modified checker_board.hpp

Added a == operator to the Checker_Board class.
Refactoring of classes.

Have the classes starting to use inheritance and breaking the classes
down including refactoring some for the Checker_Board functions. There
is now only one function for the generation of the possible moves.

Require testing.
Modified checker_board.hpp, tests.cpp, and game_piece.hpp.

Have all the tests for moves passing once again.
Addition of game.hpp and player.hpp

Adding in header files for the definitions of the base classes for
players and games to be derived from.
Adding file .gitmodules

Adding a submodule for the Catch testing framework. Will be able to
updating Catch easier.
Adding directory for the Catch framework