chore(setup.py): python 3 only now

Author: woile

setup.py

@@ -84,7 +84,7 @@ def run(self):
         # Trove classifiers
         # Full list: https://pypi.python.org/pypi?%3Aaction=list_classifiers
         'License :: OSI Approved :: MIT License',
-        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3 :: Only',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy'
     ],