Address PR feedback, add a comment to inspec.yml.

Signed-off-by: Stuart Paterson <spaterson@chef.io>

lib/plugins/inspec-init/templates/profiles/aws/inspec.yml

@@ -10,6 +10,8 @@ inspec_version: '~> 4'
 attributes:
 - name: aws_vpc_id
   required: false
+  # Below is deliberately left as a default empty string to allow the profile to run when this is not provided.
+  # Please see the README for more details.
   default: ''
   description: 'Optional Custom AWS VPC Id'
   type: string
@@ -17,4 +19,4 @@ depends:
   - name: inspec-aws
     url: https://github.com/inspec/inspec-aws/archive/master.tar.gz
 supports:
-  - platform: aws
+  - platform: aws