added note about nulls
added note about nulls

coopernurse/gorp,losinggeneration/gorp,go-gorp/gorp,gabelula/gorp,evenco/gorp,losinggeneration/gorp,mousesun/gorp,outdoorsy/gorp,kimxilxyong/gorp,go-gorp/gorp,japettyjohn/modl,rickb777/gorp-old2,mousesun/gorp,GeertJohan/gorp,jmoiron/modl,xiaoenai/gorp,rickb777/gorp-old2,d-g-laptev/gorp,coopernurse/gorp,evenco/gorp,outdoorsy/gorp,cortex/gorp,d-g-laptev/gorp,japettyjohn/modl,jmoiron/modl,xiaoenai/gorp,kevinc0825/gorm,cortex/gorp,yp-engineering/gorp,kevinc0825/gorm,gabelula/gorp,GeertJohan/gorp,kimxilxyong/gorp,yp-engineering/gorp