[PR] Cleanup of production and local development

* [x] Reduce the requirements for each site in `sites.sls`.
* [x] Remove unnecessary config from the nginx template
* [x] Reorganize `wordpress.sls` for better management of the site loop
* [x] Add documentation throughout `wordpress.sls`
* [x] Move management of `nginx.conf` to a jinja template
* [x] Enable sendfile in production, disable in local
* [x] Move xdebug config to a template
* [x] Remove `devserver.sls` state file and use a network location check instead
* [x] Allow for custom nginx files to be defined on a per site basis.

Closes #37