STK Cat Mod {Now with 100% more git repos!}

WARNING:
I have changed enough by now that the game is getting a little unstable (random
crashes, phasing through walls if going too fast), please use with caution (and
if you find a bug, try and fix it if you can before reporting it).

What I've changed in the mod:

- You can have different default powerups (so, not POWERUP_NOTHING anymore),
  and the default powerup is now the zipper.

- You always have nitro.

- Using nitro gives you nitro, instead of taking it away (can help beating
  nitro collecting levels).

- Nitro engine force and mult are multiplied by 2.5 each.

- There is no more auto rescue, use backspace instead.

- The speed limit is practically removed (set to the highest float possible)

- The zipper powerup is VERY fast now, test it in the story mode level select level first.