Update README to reflecto possible error when compiling python gdal lib on osx
Update README to reflecto possible error when compiling python gdal lib on osx

bloomberg/cartodb,UCL-ShippingGroup/cartodb-1,nuxcode/cartodb,thorncp/cartodb,dbirchak/cartodb,bloomberg/cartodb,nyimbi/cartodb,codeandtheory/cartodb,nuxcode/cartodb,splashblot/dronedb,nyimbi/cartodb,DigitalCoder/cartodb,nyimbi/cartodb,codeandtheory/cartodb,CartoDB/cartodb,raquel-ucl/cartodb,dbirchak/cartodb,UCL-ShippingGroup/cartodb-1,nuxcode/cartodb,bloomberg/cartodb,codeandtheory/cartodb,splashblot/dronedb,CartoDB/cartodb,DigitalCoder/cartodb,DigitalCoder/cartodb,CartoDB/cartodb,raquel-ucl/cartodb,UCL-ShippingGroup/cartodb-1,DigitalCoder/cartodb,future-analytics/cartodb,thorncp/cartodb,thorncp/cartodb,codeandtheory/cartodb,splashblot/dronedb,nyimbi/cartodb,DigitalCoder/cartodb,CartoDB/cartodb,nyimbi/cartodb,dbirchak/cartodb,nuxcode/cartodb,splashblot/dronedb,codeandtheory/cartodb,future-analytics/cartodb,thorncp/cartodb,future-analytics/cartodb,raquel-ucl/cartodb,CartoDB/cartodb,UCL-ShippingGroup/cartodb-1,UCL-ShippingGroup/cartodb-1,raquel-ucl/cartodb,dbirchak/cartodb,raquel-ucl/cartodb,future-analytics/cartodb,dbirchak/cartodb,future-analytics/cartodb,bloomberg/cartodb,splashblot/dronedb,thorncp/cartodb,bloomberg/cartodb,nuxcode/cartodb