v5 - Powerups

I added powerups! powerups are effectively guns you can pick up. They have a limited amount of ammo and when you run out it returns you to the basic attack.

Machine gun:  Rapidly shoot bullets

Laser: Shoot a laser, multi-hit!

Shotgun: Many bullets


I also re-did the spawning system to improve progression.

And there's a death jingle that plays now!