Edit Question With AJAX

* add: edit_question_spec.rb
* add: scenario 'Unauthenticated user tries to edit question'
* add: q<->user assosiations
* add: edit link
* add: scenario 'tries to edit his question'
* add: The action 'update' could not be found for QuestionsController
* add: update.js.erb
* add: js: true
* add: specs for question#update
* add: question#update
* add: content for update.js.erb
* add: _question
* add: .question-errors
* add: .question-edit
* add: show/hide edit-question form