Twitter subspec structure to handle reverse auth.
Twitter reverse auth using Accounts.framework.

Picks the first twitter account if exists otherwise it prompts the user to
accept the app & it creates the account using Accounts.framework.
Login with Twitter against Auth0 API.
Show ActionSheet to select twitter account.
Add objects to hold user's info and token.
Handle twitter login cancelled.
Show loading when using small social auth view
Trim username in Login/Signup/Reset Password