chore: rubocop

chore: fix api test conventions

chore: rubocop -A spec/

chore: more rubocop -A

fix failing test

rubocop fixes

removes helper methods that are in my opinion dead code

more rubocop fixes

rubocop -a --auto-gen-config

db/migrate/20170801000000_create_mail_delivery_status.rb

@@ -2,8 +2,8 @@ class CreateMailDeliveryStatus < ActiveRecord::Migration[4.2]
   def change
     create_table :mail_delivery_status do |t|
       t.datetime :created_at
-      t.string :email, :null => false
-      t.string :message, :null => false
+      t.string :email, null: false
+      t.string :message, null: false
       t.string :attachment_mime
       t.binary :attachment_data, limit: 16.megabyte