How do I create a plain text email template?

When I go to create an email template in ACS I do not have the two 'Body' fields (on for for HTML and one for Plain Text) as shown here: http://docs.appcelerator.com/platform/latest/#!/guide/Managing_Email_Templates. And when I specify the content_type : 'plain' in my Cloud.Emails.send() method I get: Error: Missing plain text format email body