Added Snail Jump/Fall in Air mockups

Figured that this mockup can serve as both the falling and jumping in
the air sprite.
-Travis
Updated Snail Jump/Falling in Air

Added the mockup in the mockups folder, made slight tweaks to previous
version.
-Travis
AI File update

Didn't get put in last commit, oops.
-Travis
So I was totally wrong

Turns out that the jumping and falling sprite being the same just looks
odd. Created a falling sprite for the snail. This looks much better.
Mockups are revised and up. Also created the sprites for zero. Putting
them in the game next.
-Travis