Rangefinder reporting

                distance                  : distance in meters (float)
                voltage                   : raw voltage if available, zero otherwise (float)

def rangefinder_send(self, distance, voltage, force_mavlink1=False):
                '''
                Rangefinder reporting

                distance                  : distance in meters (float)
                voltage                   : raw voltage if available, zero otherwise (float)

                '''
                return self.send(self.rangefinder_encode(distance, voltage), force_mavlink1=force_mavlink1)