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/aiohttp/simple_server.py

@@ -1,10 +1,13 @@
 # Run with python3 simple_server.py PORT
 
-from aiohttp import web
 import asyncio
 import sys
-import uvloop
+
 import ujson as json
+import uvloop
+
+from aiohttp import web
+
 
 loop = uvloop.new_event_loop()
 asyncio.set_event_loop(loop)