Code documentation added. Written by Michael.

Documentation for the game_controllers module has been written. (Support #205)
Code documentation added. Written by Michael.

Documentation for the game module has been added. (Support #205)
Code documentation added. Written by Michael.

Documentation for the Game of Life data structure modules; namely the cell,
grid and states modules, added. Also replaced single quotation marks with
double quotation marks in several modules. (Support #205)