Add a time estimate for the tutorial, and switch the base image from ubuntu to busybox.

static/tutorial/create-container.html

@@ -3,7 +3,7 @@
 <p>First we'll create a container with a single new file based off of the <code>ubuntu</code> base image:</p>
 
 <pre class="command">
-<code ng-show="tour.tourScope.showSudo">sudo </code>docker run ubuntu echo "fun" > newfile
+<code ng-show="tour.tourScope.showSudo">sudo </code>docker run busybox echo "fun" > newfile
 </pre>
 
 <p>The container will immediately terminate (because its one command is <code>echo</code>), so we'll use <code>docker ps -l</code> to list it:

static/tutorial/welcome.html

@@ -8,3 +8,5 @@
 <li>Changing a repository's permissions</li>
 </ul>
 </p>
+
+<p>This tutorial should take about <b>15 minutes</b>, but may take slightly longer depending on the speed of your internet connection</p>