Emphasize form of coordinates in README
Emphasize form of coordinates in README

Looking through the README, the only mention of the format of `coordinates` was under the MongoDB section which is all the way at the bottom of the file.
rdlugosz/geocoder,boone/geocoder,tiramizoo/geocoder,mdebo/geocoder,sjaveed/geocoder,AndyDangerous/geocoder,donbobka/geocoder,rios1993/geocoder,ankane/geocoder,Devetzis/geocoder,brian-ewell/geocoder,alexreisner/geocoder,moofish32/geocoder,FanaHOVA/geocoder,aceunreal/geocoder,TrangPham/geocoder,rayzeller/geocoder