one more phame tweak for better social sharing -- make sure $uri is the full uri

Summary: basically when we're on a page we have a URIPath so set that and pass it over. I wasn't super duper happy with this but it seems to be the best way to pass this data.

Test Plan: verified the og:url was correct on my dev instance of phacility blog for both the main blog and individual post view

Reviewers: epriestley

Reviewed By: epriestley

CC: chad, aran, Korvin

Differential Revision: https://secure.phabricator.com/D4269