requirements.txt is not configured properly

the leading comment seems to cause an issue with pbr.
also adding in d2to1 and pbr versions to requirements.

Change-Id: I334d928b8a575522e3879f07d578be39890712b5
Fixes: bug 1192351

requirements.txt

@@ -1,4 +1,5 @@
-# This file is managed by openstack-depends
+d2to1>=0.2.10,<0.3
+pbr>=0.5.16,<0.6
 argparse
 httplib2
 iso8601>=0.1.4

setup.py

@@ -17,5 +17,5 @@
 import setuptools
 
 setuptools.setup(
-    setup_requires=['d2to1>=0.2.10,<0.3', 'pbr>=0.5,<0.6'],
+    setup_requires=['d2to1>=0.2.10,<0.3', 'pbr>=0.5.16,<0.6'],
     d2to1=True)