website: update upgrade guide for number backwards incompat

website/source/upgrade-guides/0-8.html.markdown

@@ -57,6 +57,46 @@ EOF
 
 **Action:** Use heredocs or escape sequences when you have a string with newlines.
 
+## Names Cannot Start with Integers or Hyphens
+
+Names of variables, resources, modules, etc. may no longer start with
+numbers or hyphens. These will now fail at the validation step.
+
+This change was necessary to remove ambiguities from parsing the
+interpolations. Most languages do not allow identifiers starting with
+these characters with good reason. We now follow that as well.
+
+An example of a configuration that no longer works:
+
+```
+variable "1x1" {}
+```
+
+This must now be changed to start with a letter or underscore:
+
+```
+variable "foo-1x1" {}
+variable "_1x1" {}
+```
+
+And so on...
+
+If you're changing resource names, this can cause Terraform to consider it
+a new resource and plan to destroy it. To work around these scenarios,
+please use the `terraform state mv` command:
+
+```
+terraform state mv aws_instance.1x1 aws_instance.foo-1x1
+```
+
+The `terraform state mv` command creates a backup for each operation,
+but to be safe you can still back up your state prior to doing these
+changes.
+
+**Action:** Rename variable, resources, modules, providers, outputs that
+start with a number or hyphen. If you rename a resource or module, use
+`terraform state mv` to fix the state.
+
 ## Math Order of Operations
 
 Math operations now follow standard mathematical order of operations.