Moved DrivetrainWriter from y2017

Change-Id: If7b65b42950c51954f00f8365d5c175fe6e0aa50
diff --git a/y2017/BUILD b/y2017/BUILD
index e88c725..8637eed 100644
--- a/y2017/BUILD
+++ b/y2017/BUILD
@@ -73,6 +73,7 @@
         "//frc971/wpilib:buffered_pcm",
         "//frc971/wpilib:dma",
         "//frc971/wpilib:dma_edge_counting",
+        "//frc971/wpilib:drivetrain_writer",
         "//frc971/wpilib:encoder_and_potentiometer",
         "//frc971/wpilib:interrupt_edge_counting",
         "//frc971/wpilib:joystick_sender",