fixed startup issues

copy pasted some code from public bot code
added difference information to README.md

src/main/java/me/polymarsdev/sokobot/util/GameUtil.java

@@ -71,6 +71,7 @@ public class GameUtil {
                     Game game = games.get(playerId);
                     long timeDifference = now - game.lastAction;
                     if (timeDifference > 10 * 60 * 1000) {
+                        System.out.println("[INFO] Stopped inactive game of " + playerId);
                         game.stop();
                         GameUtil.removeGame(playerId);
                     }
@@ -78,4 +79,4 @@ public class GameUtil {
             }
         }, 10 * 60 * 1000, 60 * 1000);
     }
-}
+}