setup.py: drop python3.5 support

Since not tests are run for 3.5 drop support
with the next release.
Also Python 3.5 has reached end-of-life on 5-Sep-2020.
Python 3.5.10 is the final release of 3.5.
https://www.python.org/downloads/release/python-3510/

setup.py

@@ -29,14 +29,13 @@
     description='lightweight Disqus alternative',
     long_description=long_description,
     long_description_content_type='text/markdown',
-    python_requires='>=3.5',
+    python_requires='>=3.6',
     classifiers=[
         "Development Status :: 4 - Beta",
         "Topic :: Internet",
         "Topic :: Internet :: WWW/HTTP :: HTTP Servers",
         "Topic :: Internet :: WWW/HTTP :: WSGI :: Application",
         "License :: OSI Approved :: MIT License",
-        "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",