Takes one drive "step" in reverse to correct for the set heading. This function only works when called inside of a loop.
reverse_step(speed, desired_angle, max_speed=127)
speed: Drive speed between 0 and 127; must be below the max_speed
desired_angle: heading (0 degrees is defined when the Zumi object is created.)
max_speed: Caps the max speed. Default to 127.