Content update

The new update adds some useful gear to help you fight the zombie horde:
- Chainsaw
- Freeze gun
- Blaster
- Grenades
- Landmines
- Electro barricades
- Upgraded turrets

It also includes a lot of rendering optimizations that allowed some balance changes:
- There can now be up to 50% more zombies on screen at the same time
- Zombies get tougher at a slower rate than before
- Basic turret's cost reduced to $6000

Apologies to everyone who waited for the update for too long and hopefully next time the wait will be much shorter!