Updates to art, input, and physics

Changes made

• Swapped out the pipe sprite with one made using 3D software
• Changed semantic versioning to reflect that this is truly the prototyping stages
• Added support for touch-screen input
• Changed bird physics, so that it doesn't go up as strongly
• Fixed the hit-boxes on pipes
• Made it so that the space bar can start and restart the game, and esc brings player back to start screen.

Future Work

• Fix lag issue on touch-input (maybe change frame rate?)
• Add in high score
• Create better cloud art
• Implement particle system for cloudy background in a way that doesn't obscure bird
• Make pipe speed gradually increase over time