Change usages of xrange() to range()

In Python3, range() creates a generator rather than a list.

None of the parameters in the ranges changed looked large enough
to create an impact in memory in Python2.  Note: the only use of
range() was for iteration and did not need to be changed.

This is part of a series of changes to introduce Python3 support.

Change-Id: I50b665f9296ea160a5076c71f36a65f76e47029f
diff --git a/git_config.py b/git_config.py
index 6589b19..645c97a 100644
--- a/git_config.py
+++ b/git_config.py
@@ -168,7 +168,7 @@
       elif old != value:
         self._cache[key] = list(value)
         self._do('--replace-all', name, value[0])
-        for i in xrange(1, len(value)):
+        for i in range(1, len(value)):
           self._do('--add', name, value[i])
 
     elif len(old) != 1 or old[0] != value: