Require python >= 3.3

This avoid having a python2 pip pulling our python3 only package.

__pkginfo__.py

@@ -60,6 +60,6 @@ if os.name == 'nt':
 
 classifiers = ["Topic :: Utilities",
                "Programming Language :: Python",
-               "Programming Language :: Python :: 2",
                "Programming Language :: Python :: 3",
+               "Programming Language :: Python :: 3 :: Only",
                ]

setup.py

@@ -48,6 +48,7 @@ setup(
     classifiers=pkginfo['classifiers'],
     packages=find_packages(exclude=['contrib', 'docs', 'test*']),
     namespace_packages=[pkginfo['subpackage_of']],
+    python_requires='>=3.3',
     install_requires=pkginfo['install_requires'],
     tests_require=pkginfo['tests_require'],
     scripts=pkginfo['scripts'],