Tuned drivetrain, fixed --plot flag, and enabled closed loop drive.

Change-Id: Ib322da54e1d801e99b6a0e779468160b57eb7739
diff --git a/y2016/control_loops/python/drivetrain.py b/y2016/control_loops/python/drivetrain.py
index c5782c9..47787d4 100755
--- a/y2016/control_loops/python/drivetrain.py
+++ b/y2016/control_loops/python/drivetrain.py
@@ -73,7 +73,7 @@
     # Free Current in Amps
     self.free_current = 4.7 * self.num_motors
     # Moment of inertia of the drivetrain in kg m^2
-    self.J = 2.8
+    self.J = 2.0
     # Mass of the robot, in kg.
     self.m = 68
     # Radius of the robot, in meters (requires tuning by hand)