Make the version returned by the extension be the pbr version.

Let's not manage 2 versions in the files.

Change-Id: I22113ed0837ee49ef0ec90411cc0626dbbbbc304

os_api_ref/__init__.py

@@ -509,4 +509,4 @@ def setup(app):
     # _static directory during final build.
     app.connect('build-finished', copy_assets)
 
-    return {'version': '0.1'}
+    return {'version': __version__}