Add GPLv3.

Also, use https rather than http to access upstream.

setup.py

@@ -31,7 +31,7 @@ setup(
     version='0.1',
     author='Nexedi',
     author_email='vincent@nexedi.com',
-    url='http://lab.nexedi.com/vpelletier/python-munnel', # TODO: relocate to /nexedi
+    url='https://lab.nexedi.com/vpelletier/python-munnel', # TODO: relocate to /nexedi
     license='GPLv3',
     platforms=['any'],
     install_requires=['python-libmilter'],