Switch to new Framework :: Zope :: 3 classifier

See zopefoundation/z3c.authviewlet#6 (comment)
for the background behind this.

setup.py

@@ -44,7 +44,7 @@ def read(*rnames):
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Environment :: Web Environment',
-        'Framework :: Zope3',
+        'Framework :: Zope :: 3',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: Zope Public License',
         'Natural Language :: English',