fixed bugs:
-speeding up to max speed after first food
-not going back to initial speed on gameover
changed gridsize to 20x20;
fixed bugs:
-drawing the head of previous snake after clearScreen after gameOver
-starting with previous direction after gameOver
changed gridsize to 20x20;
changed initial speed to 180;
changed min speed to 10;
fixed bugs:
-added direction check before tail removal (stopped flashing when dir is 0,0... don't know how that resolved it...)