Update docs about Elasitcsearch 2 compatibility.
Update docs about Elasitcsearch 2 compatibility.

apinf/api-umbrella,NREL/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,NREL/api-umbrella,NREL/api-umbrella,NREL/api-umbrella