Drop mention of Python 2 support in setup.py

Author: StevenMaude

setup.py

@@ -11,8 +11,7 @@
         "Intended Audience :: Developers",
         "License :: OSI Approved :: MIT License",
         "Programming Language :: Python",
-        "Programming Language :: Python :: 2.7",
-        "Programming Language :: Python :: 3.5",
+        "Programming Language :: Python :: 3",
     ],
     requires=["setuptools"],
     keywords='autoversion __autoversion__ __version__ __version__tuple__ version git',