Sprites can be auto-generated, collisions work

Sprites have been reconfigured.
Here's the intended flow: To generate a fresh set of car sprites, simply
run the render.py (check file for usage). Then, use a program like
ImageMagick to autocrop (I used mogrify -trim +repage *.png). Then pack
the images together with TexturePacker. After this, convert the
outputted JSON using the JSON conversion script in the images directory.

I also added some basic error-checking on server.js so it doesn't crash
all the time, and when it does, it doesn't keep connections open. Should
add a constant polling if it is unable to establish a server connection.