Added segmented control to section for subsection functionality

Closes #74 #65 

Implemented the segmented control for subsections which is used with Followers and Comments.  I also had to implement Followers (API through to UI) so that I could test the data switch and data storage mechanisms for the table.  There is still a lot of duplication in logic in the `UITableViewController` subclass but that's easy enough to remove before the implementation is feature complete.
Maybe a couple constants?