add url, maintainer and maintainer_email in setup.py.

setup.py

@@ -31,6 +31,9 @@ setup(
   entry_points={
      'zc.buildout.extension': ['extension = %s:extension' % name],
      },
+  url='https://lab.nexedi.com/nexedi/slapos.rebootstrap',
+  maintainer='Kazuhiko Shiozaki',
+  maintainer_email='kazuhiko@nexedi.com',
   license='ZPL 2.1',
   include_package_data=True,
   namespace_packages=['slapos'],