Create requests-async based TestClient, remove aiohttp dependency, drop Python 3.5

Update all tests to be compatible with requests-async
Cleanup testing client changes with black and isort
Remove Python 3.5 and other meta doc cleanup
rename pyproject and fix pep517 error
Add black config to tox.ini
Cleanup tests and remove aiohttp
tox.ini change for easier development commands
Remove aiohttp from changelog and requirements
Cleanup imports and Makefile

tests/performance/wheezy/simple_server.py

@@ -2,15 +2,16 @@
 """ Minimal helloworld application.
 """
 
-from wheezy.http import HTTPResponse
-from wheezy.http import WSGIApplication
+import ujson
+
+from wheezy.http import HTTPResponse, WSGIApplication
 from wheezy.http.response import json_response
 from wheezy.routing import url
 from wheezy.web.handlers import BaseHandler
-from wheezy.web.middleware import bootstrap_defaults
-from wheezy.web.middleware import path_routing_middleware_factory
-
-import ujson
+from wheezy.web.middleware import (
+    bootstrap_defaults,
+    path_routing_middleware_factory,
+)
 
 
 class WelcomeHandler(BaseHandler):