Add note about MaxMind config (specify service).
Add note about MaxMind config (specify service).

davydovanton/geocoder,boone/geocoder,3mundi/geocoder,sr-education/geocoder,rdlugosz/geocoder,ankane/geocoder,guavapass/geocoder,jgrciv/geocoder,rayzeller/geocoder,epyatopal/geocoder,StudioMelipone/geocoder,andreamazz/geocoder,TrangPham/geocoder,mdebo/geocoder,malandrina/geocoder,sideci-sample/sideci-sample-geocoder,jaigouk/geocoder-olleh,sjaveed/geocoder,rios1993/geocoder,FanaHOVA/geocoder,tiramizoo/geocoder,AndyDangerous/geocoder,GermanDZ/geocoder,moofish32/geocoder,gogovan/geocoder-olleh,crdunwel/geocoder,donbobka/geocoder,jaigouk/geocoder-olleh,Devetzis/geocoder,eugenehp/ruby-geocoder,gogovan/geocoder-olleh,alexreisner/geocoder,tortuba/geocoder,mehlah/geocoder,mveer99/geocoder,aceunreal/geocoder,ivanzotov/geocoder,brian-ewell/geocoder