Added help text to explain that an index is required to take advantage of the bounding box optimisation
Added help text to explain that an index is required to take advantage of the bounding box optimisation

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