Convert imu_values to event loops.

Change-Id: Ia31a022550ef076526e2198e1dbf60570caf6a16
diff --git a/frc971/wpilib/ADIS16448.cc b/frc971/wpilib/ADIS16448.cc
index aec4d4f..75f082d 100644
--- a/frc971/wpilib/ADIS16448.cc
+++ b/frc971/wpilib/ADIS16448.cc
@@ -123,6 +123,8 @@
     : event_loop_(event_loop),
       joystick_state_fetcher_(event_loop_->MakeFetcher<::aos::JoystickState>(
           ".aos.joystick_state")),
+      imu_values_sender_(
+          event_loop_->MakeSender<::frc971::IMUValues>(".frc971.imu_values")),
       spi_(new frc::SPI(port)),
       dio1_(dio1) {
   // 1MHz is the maximum supported for burst reads, but we
@@ -241,7 +243,7 @@
       }
     }
 
-    auto message = imu_values.MakeMessage();
+    auto message = imu_values_sender_.MakeMessage();
     message->fpga_timestamp = ::aos::time::DurationInSeconds(
         dio1_->ReadRisingTimestamp().time_since_epoch());
     message->monotonic_timestamp_ns =