Do not add PictureRequestSecurity middleware after ActionDispatch::St…

…atic

ActionDispatch::Static is not available on production systems by default.

lib/alchemy/engine.rb

@@ -25,7 +25,7 @@ class Engine < Rails::Engine
     end
 
     initializer 'alchemy.picture_request_security' do |config|
-      config.middleware.insert_after ActionDispatch::Static, Alchemy::Middleware::PictureRequestSecurity
+      config.middleware.use Alchemy::Middleware::PictureRequestSecurity
     end
 
     initializer 'alchemy.flash_cookie' do |config|