This reverts commit fa99a21.

It causes problems, if you have an app like this

    class FooApp < Sinatra::Base
      get "/" do
        "hello foo"
      end
    end

and map it like this in config.ru

    map("/foo") { run FooApp.new }

GET /foo returns 404, which was not the case before.
GET /foo/ does reach the app.