Updated to manage for changes in optional core data values
Minor change to advance function call
In process changes to make UserManager the mediator between GithubAPI and AppDelegate, also GithubAPI and CoreData
Updates for Joe's comments prior to pull request being merged.
Missed a comment from Joe in the AppDelegate! Fixed now.
updated for a comment I've added in User+GithubConverter
Merge pull request #27 from flatiron-school/UserManagerAsMediator

User manager as mediator