changed sample URL to public data Firebase
changed sample URL to public data Firebase

ObjSal/geofire-objc,firebase/geofire-objc,firebase/geofire-objc,victoraliss0n/geofire-objc,victoraliss0n/geofire-objc,victoraliss0n/geofire-objc,ObjSal/geofire-objc,ObjSal/geofire-objc,firebase/geofire-objc,firebase/geofire-objc