Added logic to only launch login screen if user isn't already logged in
Connected UI items to code; refactored method to open signup screen
Added necessary CloudKit functions to AppDelegate
Configured login process in code
Configured code for sign up
Updated login and sign up processes to confirm whether or not user is logged in and dismiss view controllers based on the user's account state. Added UserDefaultsKeys.swift to manage NSUserDefaults key value storage.
Fixed bug with sign up process. Sign up and log in both work as expected.