Nginx listens publicly on 2087/2083 and reverse-proxies to 127.0.0.1:4000.
Previously both Nginx and Node.js were trying to bind port 2087 causing the
nixpanel service to crash-loop. HOST changed to 127.0.0.1 so the API is
not directly reachable from outside.
Bumps version to 0.3.1.