Made a small tweak to the oauth object reference in `set_page_token`

Will this actually fix anything?  I don't know but it's in the page token stuff and it's the only place I referenced the object directly instead of the function.

Related:
https://github.com/misterbisson/bsocial/pull/30

Issue:
https://github.com/GigaOM/gigaom/issues/4769