Version 1.1.3 "mag-ma-ficent" released

This version brings the following changes and additions:

• Due to volcanic activity, in some places the floor is now lava. Beware of fast descents into unknown...
• Implemented jump buffering and ledge assist. Jump buffering means pressing a jump button counts even if it was pressed a few frames before landing on ground. Ledge assist means a jump can be performed several frames after walking off a ledge.
• Added difficulty levels. Higher difficulty levels increase maze size but also increase oxygen tank maximum size and chance to spawn extra oxygen. Maze size growth is geometric while oxygen increase is linear, so chances of dying are higher.
• Some minor changes to layouts (in addition to lava pools).