FIX: disable x accl redirect for CDN assets

We need to keep headers in tact

lib/middleware/optional_sendfile.rb

@@ -0,0 +1,11 @@
+module Middleware
+  class OptionalSendfile < Rack::Sendfile
+    def call(env)
+      if env["_disable_accl"] == true
+        @app.call(env)
+      else
+        super(env)
+      end
+    end
+  end
+end