Revert to direct firebase calls (#1822)
Revert to direct firebase calls (#1822)

Tested on node v9.4.0/v9.11.2/v10.9.0 manual/regular
PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs