Author overlay part deux

We're in the process of removing the concept of author group from the application.

https://www.pivotaltracker.com/story/show/79384948
hmmm, notice that `set_position` is an attribute which is never serialized from the server but is included as a parameter for updates.  I agree that the pattern is unusual, but I'm in an after lunch coma right now and unwilling to reason further.