Update setup classifiers to be only Python 3

Author: Harmon758

setup.py

@@ -45,12 +45,11 @@
         "Operating System :: Microsoft :: Windows",
         "Operating System :: MacOS :: MacOS X",
         "Programming Language :: Python",
-        "Programming Language :: Python :: 2",
-        "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3 :: Only",
     ],
     long_description=long_description,
     long_description_content_type='text/markdown',