Added a retrieve method

This will let you get the speed from the motor directly without the
future communication system being needed

src/core/logic/motor.rs

@@ -40,6 +40,12 @@ impl<T: motor::Driver + motor::Sensor> Controller<T> {
             .set_speed_and_direction(motor_command, self.current_direction);
     }
 
+    ///Retrieve the speed from the motor inside the controller.
+    /// This allows you to get a speed value from behind the move.
+    pub fn retrieve(&self) -> motor::Speed {
+        self.motor.get_speed()
+    }
+
     ///Creates a new Controller with a motor (of type T), a max speed and a pid::Config
     /// This then allows for you to use the controller with the provided types
     pub fn new(motor: T, max_speed: Speed, config: pid::Config) -> Self {