[DOC] Update minimum S3 permissions
[DOC] Update minimum S3 permissions

When I used the old minimum S3 permissions, I got an error: `Statement is missing required element - Statement "Stmt1EmberCLIS3DeployPolicy" is missing "Principal" element.

This PR adds in the Principal element, based on [this documentation](http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Principal)
ember-cli-deploy/ember-cli-deploy-s3