website: update docs for virtualbox builder (some bugs)

website/source/docs/builders/virtualbox-iso.html.markdown

@@ -24,7 +24,7 @@ Ubuntu to self-install. Still, the example serves to show the basic configuratio
 
 <pre class="prettyprint">
 {
-  "type": "virtualbox",
+  "type": "virtualbox-iso",
   "guest_os_type": "Ubuntu_64",
   "iso_url": "http://releases.ubuntu.com/12.04/ubuntu-12.04.3-server-amd64.iso",
   "iso_checksum": "2cbe868812a871242cdcdd8f2fd6feb9",

website/source/docs/builders/virtualbox.html.markdown

 ---
 layout: "docs"
-page_title: "Amazon AMI Builder"
+page_title: "VirtualBox Builder"
 ---
 
 # VirtualBox Builder