Setup a production-like environment in vagrant

- We already use Daphne and channels to prepare the future use of
  websockets.
- The app is served behind an nginx reverse-proxy
- The services we need are managed by systemctl

The production-like running instance of GestionÉvénementiel can be
accessed on localhost:8080 outside vagrant.

evenementiel/asgi.py

@@ -0,0 +1,7 @@
+import os
+from channels.asgi import get_channel_layer
+
+if "DJANGO_SETTINGS_MODULE" not in os.environ:
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "evenementiel.settings")
+
+channel_layer = get_channel_layer()