Add Parse framework
Add Login and Register features

Add LoginViewController and RegisterViewController. Add UI elements to RegisterViewController and some logic to create Parse account.

TODO: Register has no exit segue, Login has nothing.
Add Login functionality

Add logic to support login in Parse. Fix some issues with registration.

TODO: automatically capitalize user’s names.
TODO: explore API to give more detailed messages (e.g. account already exists vs unable to register due to connectivity)
TODO: verify password in registration with double entry
TODO: allow cancel during registration to get to login page
TODO: verify email??