Involves adding META.json to $GITHOME with metadata about Slony http://pgxn.org/spec
Got a branch for this... https://github.com/cbbrowne/slony1-engine/tree/pgxn
Consider it to be an open question, for now, whether or not something more extensive should be done about this. It would be an interesting idea to have Slony components loaded as extensions, as this might be an easier way for users to deploy it. Details as to how this sort of thing would work will probably emerge after the release of PG 9.1, so it doesn't make sense to do anything more with this for the time being.