Move `apt-get update` after adding PPA
Specify Node.js version
Make name consistent with other steps
Update Ansible vars
Make app listen to public port

Omit hostname to ensure app is accessible via Internet, i.e. hostname MUST be
`0.0.0.0`, not `127.0.0.1`.

/cc @iangilman @kenperkins @aseemk
Use `upstart` to convert to service
Remove timeout from root path
Add health check endpoint
Leverage `upstart` respawn instead of `forever`
Use `_root` instead of `_dir` suffix