Moved from listening on localhost to `0.0.0.0` to allow port forwarding

I have `Vagrant` running but ran into a snag regarding port forwarding. Since we are using `localhost` as the `hostname`, we are only allowing connections from the same computer. To fix this, I have moved to `0.0.0.0` which allows connections from anywhere.

https://github.com/hapijs/hapi/blob/master/docs/Reference.md#createserverhost-port-options

One option is to move this into `settings.host`.

In my past experience, it is good to create a `settings.url.internal` and `settings.url.external` (and maybe a `settings.url.static` for here). It allows for the distinction of where we should be listening locally (`internal`) and where to comment about absolute URLs (`external`) (e.g. when writing to `console`).

https://github.com/twolfson/site/compare/dev/external.url