Fix some python2-isms in prep for python3

These ones should work in both versions so we don't have to do them as
part of a global change over.

Change-Id: I2177b329d385c50d706a50a750b6c115ea3ea7ae
diff --git a/y2016/control_loops/python/arm.py b/y2016/control_loops/python/arm.py
index 96975bb..9e6de34 100755
--- a/y2016/control_loops/python/arm.py
+++ b/y2016/control_loops/python/arm.py
@@ -261,7 +261,7 @@
         shooter_profile.SetGoal(goal[2, 0])
 
         U_last = numpy.matrix(numpy.zeros((2, 1)))
-        for i in xrange(iterations):
+        for i in range(iterations):
             X_hat = arm.X
 
             if observer is not None: