Added several features to agent, board and play.
Added specs to Play.
Added private attribute accessors to Agent.
Added constants to Agent.
Added uncover neighbours method to Agent with its respective specs.
Replaced make_command method in agent to use the new .to_command method in Play.
Fixed each_neighbour to yield only the last charcacter of the cell.
The client is now capable of playing an entire game uncovering the neighbours of each adjacent cell recursively.