Made KF data available to polydrivetrain.

Change-Id: I067d0d05b9fc32d6ad50fbd35a6e9ad07b63f20d
diff --git a/y2014/control_loops/drivetrain/polydrivetrain.cc b/y2014/control_loops/drivetrain/polydrivetrain.cc
index 16ca10a..02d0658 100644
--- a/y2014/control_loops/drivetrain/polydrivetrain.cc
+++ b/y2014/control_loops/drivetrain/polydrivetrain.cc
@@ -23,8 +23,9 @@
 using ::y2014::control_loops::CIMLogging;
 using ::frc971::control_loops::CoerceGoal;
 
-PolyDrivetrain::PolyDrivetrain()
-    : U_Poly_((Eigen::Matrix<double, 4, 2>() << /*[[*/ 1, 0 /*]*/,
+PolyDrivetrain::PolyDrivetrain(StateFeedbackLoop<7, 2, 3> *kf)
+    : kf_(kf),
+      U_Poly_((Eigen::Matrix<double, 4, 2>() << /*[[*/ 1, 0 /*]*/,
                /*[*/ -1, 0 /*]*/,
                /*[*/ 0, 1 /*]*/,
                /*[*/ 0, -1 /*]]*/).finished(),