* Add basic coverage for settings/exports controller
* Remove unused @account variable from settings/exports controller
* Add coverage for download export actions
* Remove deprecated `render :text` in favor of `send_data` for csv downloads
* Add model to handle exports
* Use Export class in settings/exports controller
* Simplify settings/exports controller methods
* Move settings/export to more restful routes
Akihiko Odaki (@fn_aki@pawoo.net)