Fix z-ordering of Facebook Like flyout.
Fix z-ordering of Facebook Like flyout.

The social/about links appear under the Popular Photos panel, but the
Like flyout appears above it.

See #49

danvk/oldnyc,danvk/oldnyc,nypl-spacetime/oldnyc,nypl-spacetime/oldnyc,nypl-spacetime/oldnyc,nypl-spacetime/oldnyc,luster/oldnyc,danvk/oldnyc,nypl-spacetime/oldnyc,luster/oldnyc,danvk/oldnyc,luster/oldnyc,luster/oldnyc,luster/oldnyc