Added login form.
Added passport strategy as local. 

* Updated User model to have roles
* Added 'contributor' role as a default when 
register a user
Added role verification for questions pages.

* Add hasRole method to User model
* Admin can view all the questions
* Contributor can add new questions
Added New Question form.

* Only admin and contributor can add a new question
* Question can be viewed by creator and/or admin