website: update docs for vsphere changes

website/source/docs/post-processors/vsphere.html.markdown

@@ -18,6 +18,8 @@ each category, the available configuration keys are alphabetized.
 
 Required:
 
+* `cluster` (string) - The cluster to upload the VM to.
+
 * `datacenter` (string) - The name of the datacenter within vSphere to
   add the VM to.
 
@@ -29,8 +31,7 @@ Required:
 * `password` (string) - Password to use to authenticate to the vSphere
   endpoint.
 
-* `path_to_resource_pool` (string) - The path within the resource pool to
-  store the VM.
+* `resource_pool` (string) - The resource pool to upload the VM to.
 
 * `username` (string) - The username to use to authenticate to the vSphere
   endpoint.