Major / minor change note 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/93511/5068361/602372ca-6e45-11e4-9079-36a10250ee52.png)