respect the virtualenv by using /usr/bin/env

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
diff --git a/planetstack/util/logger.py b/planetstack/util/logger.py
index a5b2a46..e4137e7 100644
--- a/planetstack/util/logger.py
+++ b/planetstack/util/logger.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 #----------------------------------------------------------------------
 # Copyright (c) 2008 Board of Trustees, Princeton University