Add Warrior class and modules

- Warrior class holds the RubyWarrior::Turn instance and works with it
- RubyWarrior::Turn instance must be updated every turn
- Warrior::Health module holds health related methods
- Warrior::Sight module holds sensory related methods
- Warrior::Brains module will hold most logic methods, when Warrior becomes smarter
- Removed all logic from Player#play_turn, which was turning quite hugly