Create RemoteTranslations Controller

- Create RemoteTranslations Controller to receive resources without
  translations and create RemoteTranslation instances when theirs
  translations are not enqueued.
- Create remote_translation_enqueued? class method on RemoteTranslation
  model to check if exists same remote translations without errors
  pending to translate.

config/routes.rb

@@ -42,6 +42,7 @@ Rails.application.routes.draw do
   resources :images, only: [:destroy]
   resources :documents, only: [:destroy]
   resources :follows, only: [:create, :destroy]
+  resources :remote_translations, only: [:create]
 
   # More info pages
   get "help",             to: "pages#show", id: "help/index",             as: "help"