Fixed some consistency issues.

- Get the root URLs from the configuration. The defaults will be automatically provided by WinterSmith if not present in `config.json`.

- Removed some unnecessary whitespace / indentation in the file.

- Used roots.output in production.

A special note here is that the defaults provided by the old code were using strings such as `/contents` which resolve to the root directory on UNIX operating systems. It is expected to use `./contents` and `./build` - which are the defaults provided by WinterSmith anyway.