Use player display_name

app/models/play.rb

@@ -16,7 +16,7 @@ class Play < ActiveRecord::Base
   def check_for_winner
    if self.game.over?
      self.game.winner_player_id = self.player.id
-     self.game.status = "Player #{self.player.id} wins!"
+     self.game.status = "Player #{self.player.display_name} wins!"
      self.game.save
    end
   end