Explain major and minor for publishing

As Users now have change notes, we should probably explain what type of change it is and what impact publishing will have. [Ticket](https://trello.com/c/mUPdaenr/426-minor-major-edits-confirmation-on-publish-2). 
Worked on this with @futurefabric.

Screenshot:
![screen shot 2014-12-05 at 16 05 32](https://cloud.githubusercontent.com/assets/449004/5318622/4077e58e-7c99-11e4-9d24-e9726258b581.png)
From my reading this is still going to have a class of `panel-danger` on a minor edit. Do we want to differentiate between the two in the panel class too?