Update setup.py classifiers to indicate that Python3 is supported.

Author: fviard

setup.py

@@ -97,9 +97,14 @@
         'Operating System :: Microsoft :: Windows',
         'Operating System :: POSIX',
         'Operating System :: Unix',
+        'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.6',
         'Programming Language :: Python :: 2.7',
-        'Programming Language :: Python :: 2 :: Only',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.3',
+        'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
         'Topic :: System :: Archiving',
         'Topic :: Utilities',
     ],