After upgrading to rails3.2.1,this warning occurs:
You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released
I move my plugins in vendor/plugins directory but i don't know how to write config/initializers/myplugin.rb file, and google can't find the answer.
I just wrote a blog post on this: How to Convert Simple Rails 2.3 Style Plugins for Rails 3.2