Update polymer tutorial; make directory paths match new sample structure

src/site/docs/tutorials/httpserver/index.markdown

 ---
 layout: tutorial
 title: "Write HTTP Clients & Servers"
 description: "Communicate over the internet"
 has-permalinks: true
 tutorial:
   id: httpserver
 next: 
 next-title: "Home" 
 prev: cmdline/
 prev-title: "Write Command-Line Apps"
 header:
   css: ["/docs/tutorials/httpserver/httpserver.css"]
 ---
 
 {% capture whats_the_point %}
 
 * Knowledge of Futures and Streams is a prerequisite.
 * The HTTP protocol allows clients and servers to communicate.
 * The dart:io package has classes for writing HTTP programs.
 * Servers listen for requests on a host and port.
 * Clients send requests using an HTTP method request.
 * The http_server package provides higher-level building blocks.
 
 {% endcapture %}
 
 {% capture sample_links %}
 
-<p> This tutorial features these examples:</p>
+This tutorial features these examples,
+which live under the **httpserver** directory:
 
 * hello_world_server.dart
 * number_thinker.dart
 * basic_writer_server.dart
 * basic_writer_client.dart
 * mini_file_server.dart
 * basic_file_server.dart
 * hello_world_server_secure.dart
 
 <p>
@@ skipping 1102 matching lines @@
 * [Get Input from a Form](/docs/tutorials/forms/) shows how to make a POST
 request from a browser-based client using an HTML form.
 It also discusses the related server.
 
 * Be sure to investigate the other packages on
 <a href="https://pub.dartlang.org/" target="_blank">pub.dartlang.org</a>.
 
 {% endcapture %}
 
 {% include tutorial.html %}