The existing documentation example looks intimidating as it includes: * variable interpolation * configuration of the chef provisioner * and it misses the `config_template` file In the issue comments, [simpler and complete example](https://github.com/hashicorp/packer/issues/3355#issuecomment-198134727) exists already and works out of the box. This change adds the simpler and complete example, while leaving the more complicated example intact.