Version 1.1 released

Version 1.1 brings the following fixes and additions:

• Fixed score award for remaining oxygen when reaching a teleport.
• Added crystals into cave layouts, collecting each awards 300 points.
• Added alien artifact spheres into cave layouts, collecting each awards 500 points.
• Each maze tile type has two more layouts to choose from, for a total of four.
• Added margins to caves (two tiles wide) so player doesn't have to walk too close to screen edges.
• Fixed display of final score in game over screen when top ten is not reached.
• Added a second tileset to bring variety to cave visuals.