Update README for master switchover.
Update README for master switchover.

ncalexan/mentat,mozilla/mentat,ncalexan/datomish,mozilla/mentat,ncalexan/mentat,mozilla/mentat,mozilla/mentat,mozilla/mentat,ncalexan/datomish,ncalexan/mentat,ncalexan/mentat,ncalexan/mentat,mozilla/mentat,ncalexan/mentat