Added new server/cmdline/io programmers' guide.

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

 ---
-layout: default
+layout: tutorial
 title: "Write Command-Line Apps"
 description: "Basics for command-line apps"
 has-permalinks: true
 tutorial:
   id: dart-io
 next: /
 next-title: "Home"
 prev: indexeddb/
 prev-title: "Use IndexedDB"
 ---
@@ skipping 616 matching lines @@
 
 ## What next? {#what-next}
 
 The [Get Input from a Form](/docs/tutorials/forms/) tutorial
 features a client-server.
 The code for the server, which uses CORS headers and handles
 POST requests, is explained in detail.
 
 {% endcapture %}
 
-{% include tutorial.html %}
+{% include tutorial.html %}