Clarify doubly-nested array use in post-processors

Expands on the description of the Vagrant and Vagrant Cloud
post-processors needing to be in a doubly-nested array.

Also, separate the two arrays in the JSON sample so they stick out more
(and reformat the JSON).

website/source/docs/post-processors/vagrant-cloud.html.markdown

@@ -78,8 +78,9 @@ the box will not be uploaded to the Vagrant Cloud.
 ## Use with Vagrant Post-Processor
 
 You'll need to use the Vagrant post-processor before using this post-processor.
-An example configuration is below. Note the use of the array specifying
-the execution order.
+An example configuration is below. Note the use of a doubly-nested array, which
+ensures that the Vagrant Cloud post-processor is run after the Vagrant
+post-processor.
 
 ```javascript
 {
@@ -91,7 +92,8 @@ the execution order.
       // ...
   }],
   "post-processors": [
-      [{
+    [
+      {
         "type": "vagrant",
         "include": ["image.iso"],
         "vagrantfile_template": "vagrantfile.tpl",
@@ -102,7 +104,8 @@ the execution order.
         "box_tag": "hashicorp/precise64",
         "access_token": "{{user `cloud_token`}}",
         "version": "{{user `version`}}"
-      }]
+      }
+    ]
   ]
 }
 ```