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/y2014/control_loops/python/claw.py b/y2014/control_loops/python/claw.py
index cade03d..346a188 100755
--- a/y2014/control_loops/python/claw.py
+++ b/y2014/control_loops/python/claw.py
@@ -401,7 +401,7 @@
     upper_bound = (initial_X[1, 0] if initial_X[1, 0] > goal[1, 0] else
                    goal[1, 0]) + max_separation_error
 
-    for i in xrange(iterations):
+    for i in range(iterations):
         U = claw.K * (goal - claw.X)
         U = ScaleU(claw, U, claw.K, goal - claw.X)
         claw.Update(U)