Add language detection (#1772)

* Add language detection via WhatLanguage and (de)serialization of it through Atom

* Fix default language in ProcessFeedService

* Re-add newline before 'react-rails' Gem to fix groupings

Fixes Code Climate issue

db/migrate/20170414132105_add_language_to_statuses.rb

@@ -0,0 +1,5 @@
+class AddLanguageToStatuses < ActiveRecord::Migration[5.0]
+  def change
+    add_column :statuses, :language, :string, null: false, default: 'en'
+  end
+end