Initial simplification of Scene logic

Using root_layer.draw() to draw all Sprites.  Eliminated enemies list.  All enemies now kill if player is falling (fixes https://github.com/tjferry14/Cloud-Jump-2/issues/19).  Added sound on new high score (fixes https://github.com/tjferry14/Cloud-Jump-2/issues/17).
Update CloudJump2.py
Merge pull request #22 from cclauss/patch-7

Initial simplification of Scene logic