Update Messaging Type for BotStack and BackChat

https://developers.facebook.com/docs/messenger-platform/send-messages#messaging_types

![Screenshot 2018-03-13 13.41.28.png](https://codetreeusercontent.s3.amazonaws.com/uploads/26e428bd-1444-46e8-a452-3955a8dff25b/Screenshot+2018-03-13+13.41.28.png)
