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/frc971/control_loops/python/controls.py b/frc971/control_loops/python/controls.py
index 7505413..defdbd2 100644
--- a/frc971/control_loops/python/controls.py
+++ b/frc971/control_loops/python/controls.py
@@ -117,7 +117,7 @@
   n = A.shape[0]
   output = B
   intermediate = B
-  for i in xrange(0, n):
+  for i in range(0, n):
     intermediate = A * intermediate
     output = numpy.concatenate((output, intermediate), axis=1)