[WIP] Feedback required on... feedback

Main thing of focus here is the way I've integrated the mailer, through a connection in the repository.
Something I discovered yesterday when looking into the flash messaging bug that might be a nice addition:

```rb
class ApplicationController < ActionController::Base
  add_flash_types :success
end

class ArticleFeedbacksController < ApplicationController
  redirect_to article_path(article.id), success: t('.flash_notice')
end
```