Add note about strictly requiring Varnish < 3.0
Add note about strictly requiring Varnish < 3.0

See #333 and #287

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