Addition of enemy collision and implementation of game over screen and platforms

My computer got all weird and acted like the control key was held down
or something and so I couldn't type many letters so I uploaded what I
was working on so this description goes for this change and the previous
change. I added collision detection with the enemies so now it will go
to the game over screen. Clicking the game over screen will reset back
to the game play mode. I also added some platform classes (although they
were just ones I made in paint so they look really bad if someone wants
to make better ones please do) and random platform spawning.