Edit Answers With AJAX

* add: acceptance_helper
* add: webkit-driver
* add: apply stash from individual lesson
* add: scenario 'invalid question'
* refact: .answer-errors
* add: scenarios for 'edit' link visibility
* add: describe 'Authenticated user'
* add: works with answers.js
* add: unique id for answer_body_create
* add: unique ids
* refact: green specs