static/ serves static files which get copied around per deploy. Since
the webpack stats files need a consistent name and change per deploy,
they can't live in static/.
This fixes a bug that preventing downgrading a Zulip server to an old
version.
This allow the webbpack dev server to properly reload JavaScript modules
while running in dev without restarting the server. We need to connect
to webpack-dev-server directly because SockJS doesn't support more than
one connection on the same host/port.
Pweaver (Paul Weaver)
Harshit Bansal
Mehanig