[importer] Make Downloader use a temporary directory
[importer] Make Downloader use a temporary directory

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