Major / minor change workflow

Adds fields for announcing major changes along with a summary of changes.
https://www.agileplannerapp.com/boards/173808/cards/6320
![screenshot - 171114 - 10 34 07](https://cloud.githubusercontent.com/assets/93511/5069385/7b52242c-6e51-11e4-95fb-f3994b41488b.png)