support of older version of aiohttp

src/risotto/http.py

@@ -161,7 +161,7 @@ async def get_app(loop):
             print(f'  - {path} (http_get)')
         print()
     del extra_routes
-    app.add_routes(routes)
+    app.router.add_routes(routes)
     await dispatcher.on_join()
     return await loop.create_server(app.make_handler(), '*', get_config()['http_server']['port'])