Async security check (#869)

Co-authored-by: Jacob Floyd <cognifloyd@gmail.com>

Fixes #868

Allow to use coroutines with Aiohttp in security handlers.

- Move all function from connexion.operations.security to a class in connexion.security.SecurityHandlerFactory
- Specialize this class for AioHttp and Flask, and instantiate them in dedicated APIs
- AioHttp specialization now support coroutines
- pass_context_arg_name option is supported for security handlers

tests/api/test_secure_api.py

@@ -1,7 +1,5 @@
 import json
 
-from connexion import FlaskApp
-
 
 def test_security_over_nonexistent_endpoints(oauth_requests, secure_api_app):
     app_client = secure_api_app.app.test_client()