Ruby Rack - mounting a simple web server that reads index.html as default

I'm trying to get some information from this tutorial: http://m.onkey.org/2008/11/18/ruby-on-rack-2-rack-builder

basically I want to have a file config.ru that tell rack to read the current directory so I can access all the files just like a simple apache server and also read the default root with the index.html file...is there any way to do it?

my current config.ru looks like this:

run Rack::Directory.new('')
#this would read the directory but it doesn't set the root to index.html


map '/' do
  file = File.read('index.html')
  run Proc.new {|env| [200, {'Content-Type' => 'text/html'}, file] }
end
#using this reads the index.html mapped as the root but ignores the other files in the directory

So I don't know how to proceed from here...

I've also tried this following the tutorials example but thin doesn't starts properly.

builder = Rack::Builder.new do

  run Rack::Directory.new('')

  map '/' do
    file = File.read('index.html')
    run Proc.new {|env| [200, {'Content-Type' => 'text/html'}, file] }
  end

end

Rack::Handler::Thin.run builder, :port => 3000

Thanks in advance