Game improvements

Summary of changes:
-Added separate layers for mountains, and temples with parallaxing effect
-Ninja jump/walking animation is now working
-Made ninja and hurdles bigger
-Made grass shorter and scrolls continuously without any gaps
-Coded logic for displaying walk images based on input from the device (this will likely have to be tweaked since it's hard to test without the actual device)
-Shrunk down asset image sizes for better memory usage

TO DO:
-Collision detection between ninja and hurdle
-More obstacles
-Levels
-Timing tweaks
-Interaction with device