Add Flash and MethodOverride middlewares only to MC engine

And not to the whole app, as these might interfere with other
middlewares such as `Rack::RewindableInput`.

Thanks to @mintuhouse for realising this. Fixes #207.

Author: rosa

lib/mission_control/jobs/engine.rb

@@ -9,8 +9,8 @@ class Engine < ::Rails::Engine
 
       initializer "mission_control-jobs.middleware" do |app|
         if app.config.api_only
-          app.middleware.use ActionDispatch::Flash
-          app.middleware.use ::Rack::MethodOverride
+          config.middleware.use ActionDispatch::Flash
+          config.middleware.use ::Rack::MethodOverride
         end
       end