respect the virtualenv by using /usr/bin/env

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
diff --git a/planetstack/xos-config.py b/planetstack/xos-config.py
index 7aa375b..e6f3d60 100755
--- a/planetstack/xos-config.py
+++ b/planetstack/xos-config.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 import sys
 from planetstack.config import Config