2.5.0

• Drop Python 2.7 support, support Python 3.8
• Convert responses to raise ProblemException (#955)
• Add error path to schema validation
• Do not sanitize body keys in OpenAPI 3 (#1008)
• Date/time serialization (#851)
• Forward options to AioHTTP app (#885)
• Returning tuples supported in AioHTTP (#849)
• Allow Swagger UI configuration options (#948)
• Remove security parameter to pass query validation (#470)
• Allow users to enable debug mode via environment variable