Add sign in, sign out and callback routes for API login.
Add dotenv and twitter keys and tokens.
Correct Dotenv.load in environment.
Add User migration and model.
Change heading for app.
Add oauth helper methods.
Add sign in button.
Change twitter user to simply users.
Add /sign_in route redirect to the request token authorize url.
Add sign in and sign out buttons.
Add session request token clear and redirect to homepage for /sign_out route.