include page json when posting fork actions

This change allows us to fork a page from
behind a firewall to an origin server outside
that firewall. Both the ruby and node servers
have had support for this for a long time.

https://github.com/fedwiki/wiki-node-server/blob/master/lib/server.coffee#L476-L479
https://github.com/fedwiki/wiki-gem/blob/master/lib/wiki/server.rb#L245-L247