Added new field for User - a name. 

* Added new field for user - a name. 
* Refactored registering so the user has to input the name (beginning with a capital letter). 
* Moved the initials of the author to user. Also added a method called author to Question so we don't have to change all the views which display author (I'm displaying user.name as author now). 
* Edited forms so the Author cannot be input now. And most of all refactored tests (added test for User which now checks most of validations on author which was tested in Question before).
It's good solution for now (because it just works :)), but for simplicity sake, I'd go for a filter in `ApplicationController` (just as the docs say: [plataformatec/devise#strong-parameters](https://github.com/plataformatec/devise#strong-parameters)):

```` ruby
class ApplicationController < ActionController::Base
  before_action :configure_permitted_parameters, if: :devise_controller?

  protected

  def configure_permitted_parameters
    devise_parameter_sanitizer.for(:sign_up) << :name
  end
end
````

This way, you don't have to subclass the default `Devise::RegistrationsController`, so we have less code to maintain :)