Added cars fade out animation

Cars now fade out when they despawn and when they reach a destination! So when I sent this to a friend they got confused why cars kept disappearing, so I added this.

When a car reaches the destination, the car will fade out green, but if the car despawns because it has no route it will fade out red. This was actually harder than it seems because my code was just basically freeing the car class as soon as the car reached the destination, but I changed the code so it would decrement a counter before deleting itself and use the counter to change the color of the car.