Move canvas state out of the Snake class.
Whitespace
Remove confusing prefix
Refactor check of insideness to use Coord objects insteaad of raw coordinates.
Whitespace
Move display of points outside snake model.
Add a comment.
Remove unecessary output
Move random coord generation to inside of coord class.
Whitespace
Unpollute the global environment with a bunch of things describing rendering and game mechanics specific to the snake.