Scroll World

Causes the world to scroll when the player nears the top of the screen.
Allow Repeated Jumping

Allows the user to hold down jump to bounce.
Change Platform Constructor to Floats

Although these will probably always be integers, the superclass uses
floats, and there's no compelling reason to be more restrictive.
(Whereas the additional restriction was causing trouble with
calculations.)
Generate New Platforms as the Level Scrolls

Adds code so that as the world scrolls, new floors to the tower appear
at the top of the screen.

KNOWN ISSUE: Old floors are never deleted. Presumably, in time, this
could cause massive memory bloat. Likely will solve this by batching
platform objects.
Remove Unused Import from Hero.hx