Merge pull request #2712 from bensojona/f-document-artifact-types

Document recommended artifact-types

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

@@ -58,9 +58,11 @@ you can also use `token` configuration option.
     You must have access to the organization—hashicorp in this example—in order
     to add an artifact to the organization in Atlas.
 
--   `artifact_type` (string) - For uploading AMIs to Atlas, `artifact_type` will
-    always be `amazon.ami`. This field must be defined because Atlas can host
-    other artifact types, such as Vagrant boxes.
+-   `artifact_type` (string) - For uploading artifacts to Atlas. `artifact_type`
+    can be set to any unique identifier, however, the following are recommended
+    for consistency - `amazon.image`, `digitalocean.image`, `docker.image`,
+    `googlecompute.image`, `openstack.image`, `parallels.image`, `qemu.image`,
+    `virtualbox.image`, `vmware.image`, `custom.image`, and `vagrant.box`.
 
 ### Optional: