Updated README to state API is only thread-safe if GEOIP_CHECK_CACHE is not used
Updated README to state API is only thread-safe if GEOIP_CHECK_CACHE is not used

borisz/geoip-api-c,Distrotech/geoip-api-c,Distrotech/geoip-api-c,Distrotech/geoip-api-c,borisz/geoip-api-c,borisz/geoip-api-c