fix calculation of displayed rating

player.py

@@ -12,7 +12,7 @@ class PlayerInLeaderboard:
         self.playerId   = playerId
         self.mu         = mu
         self.sigma      = sigma
-        self.rating     = int(self.mu) - int(self.sigma)
+        self.rating     = int(self.mu) - 2*int(self.sigma)
         self.games      = int(games)
         self.wins       = int(wins)
         self.loses      = self.games - self.wins