refactor public routes using scope
create users table
add User model
add user factory
add user spec
add users routes
add users routing spec
add Public::NewUserForm
add Public::NewUserForm spec
add errors partial
add Public::UsersController
add i18n for user
add Public::UsersController spec
add current_user helper to public::application
login user when register
add login/logout routes
add sessions routing spec
add Public::SessionsController
add logout routing spec
add Public::SessionsController spec