add: moveUntilStop method
fix: add forgotten self. in method call
add: rotateStraight method
change: Asteroid class now subclasses Movable
fix: Asteroid now really subclasses Movable
fix: added import from local package
fix: final yield to prevent StopIteration error
fix: add default value for dw
add: working rotateStraight method
fix: add yield to _moveStraight method
change: asteroid test spawning