reorganized UI flow so that sharing buttons are only displayed after heart rate event is finalized (overlay heart positioned and caption entered)
simplified code by inheriting from CBCDetailsController (details and final share view are identical, and CBCEditPhoto is also based off of it)
added NSUserDefaults so the app will remember your login credentials (unless you ask it not to do so), and whether or not you were logged in
the last time you ran... it auto logs in (with your previous creds) if appropriate