build py3 versions only.

Author: ikirudennis

setup.cfg

@@ -1,4 +1,2 @@
 [aliases]
 test=pytest
-[bdist_wheel]
-universal=1

setup.py

@@ -43,6 +43,7 @@ def get_version():
         'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3 :: Only',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
@@ -64,4 +65,5 @@ def get_version():
     cmdclass = {'test': PyTest},
     include_package_data=True,
     zip_safe=False,
+    python_requires='~=3.5',
 )