Actually run down estimator in drivetrain

Change-Id: I8602c448b632e966fe3f252b48a0f7ec0726285e
diff --git a/frc971/zeroing/imu_zeroer.h b/frc971/zeroing/imu_zeroer.h
index e95c231..5f53e0d 100644
--- a/frc971/zeroing/imu_zeroer.h
+++ b/frc971/zeroing/imu_zeroer.h
@@ -11,6 +11,8 @@
 class ImuZeroer {
  public:
   // Average 5 seconds of data (assuming 2kHz sampling rate).
+  // TODO(james): Make the gyro zero in a constant amount of time, rather than a
+  // constant number of samples...
   static constexpr size_t kSamplesToAverage = 10000.0;
 
   ImuZeroer();