Remove the social icons if no go-local-bsocial

Addresses https://github.com/GigaOM/gigaom/issues/4654

Only try to show the social icons of `go-local-bsocial` is present.

New filter that lets `go-local-bsocial` add the icons in. No `go-local-bsocial` == no icons. Works on a vanilla WP install (no breaking deps)
This isn't a permalink to the quote