Convert gyro_reading over to event loops.

LPD8806 wasn't going to fit in well, but it's never been used on a
robot.  So take the easy way out and remove it.

Change-Id: Ib4d29b40d63a8663878ff1b074057be8b2df9259
diff --git a/frc971/wpilib/gyro_sender.h b/frc971/wpilib/gyro_sender.h
index 61b7704..338ad32 100644
--- a/frc971/wpilib/gyro_sender.h
+++ b/frc971/wpilib/gyro_sender.h
@@ -32,6 +32,7 @@
   ::aos::EventLoop *event_loop_;
   ::aos::Fetcher<::aos::JoystickState> joystick_state_fetcher_;
   ::aos::Sender<::frc971::sensors::Uid> uid_sender_;
+  ::aos::Sender<::frc971::sensors::GyroReading> gyro_reading_sender_;
 
   // Readings per second.
   static const int kReadingRate = 200;