Add python_requires>=3.5

Author: Chilipp

setup.py

@@ -29,6 +29,7 @@ def readme():
         'Operating System :: OS Independent',
       ],
       keywords='sphinx autodoc autosummary content table',
+      python_requires=">=3.5",
       url='https://github.com/Chilipp/autodocsumm',
       author='Philipp S. Sommer',
       author_email='[email protected]',