Added TextPrinter, other minor adjustments

Added TextPrinter class so that I could print some text on game screen.
Added getAngle() method to Vector2 class. In SpriteRenderer I added
drawSprite method with new parameter "float angle" which will rotate
sprite. Improved gameplay by a bit, you can no longer jump two or more
times in the air. Also if runner dies, he will fall down rotating with
intertia.