added guid to bstat vars

This is needed for work in go-content-stats, see https://github.com/GigaOM/gigaom/issues/4590

Note: something about my local environment is weird, the localize script was not firing without changing the `template_redirect` priority to `9` from `15`.  This change is not included in this PR though, as it seemed to be working as is in production, so I'm assuming that is a local problem for me.