Needed to prevent connection errors if the password contains non-urlsafe characters.
Dockerfile change because all the services using it are mirroring ./ in /app now anyway.
Flower needs because it needs bookwyrm in order to read the celerywyrm config (because flower only allows overwriting broker_url from the command line and we want to do it in Python so we have access to a urlencode function).
the link to celery's homepage has been dead for at least several months
activitypub.rocks now supports tls (yay!)
the links to django's docs were for older versions of django than what bookwyrm uses
