Update rails and code

config/application.rb

@@ -1,4 +1,4 @@
-require File.expand_path('../boot', __FILE__)
+require_relative 'boot'
 
 require 'rails/all'
 
@@ -8,6 +8,9 @@ Bundler.require(*Rails.groups)
 
 module Projekteuler
   class Application < Rails::Application
+    # Initialize configuration defaults for originally generated Rails version.
+    config.load_defaults 5.1
+
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration should go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded.
@@ -20,8 +23,5 @@ module Projekteuler
     config.i18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.{rb,yml}').to_s]
     config.i18n.available_locales = :de
     config.i18n.default_locale = :de
-
-    # Do not swallow errors in after_commit/after_rollback callbacks.
-    config.active_record.raise_in_transactional_callbacks = true
   end
 end