config.rb.erb, added settings for mail notifications

ADD TO NODE LIST OR ROLE:
    "backup": {
      "notifiers": {
        "mail": {
          "on_success": "false",
          "on_warning": "true",
          "on_failure": "true",
          "from": "alerts@hostname.pro",
          "to": "alerts@hostname.pro",
          "address": "smtp.gmail.com",
          "port": "587",
          "domain": "hostname.pro",
          "user_name": "alerts@hostname.pro",
          "password": "Change password",
          "authentication": "plain",
          "encryption": ":starttls"

        }
I don't access the 'node' at all from ERB Templates in my cookbook.  If you want me to accept this pull request I would ask you to transition to how I handle erb variables in the same file.

Thanks.