update ordering filter to work with drf 3.5.x
update ordering filter to work with drf 3.5.x

openaid-IATI/OIPA,openaid-IATI/OIPA,zimmerman-zimmerman/OIPA,zimmerman-zimmerman/OIPA,openaid-IATI/OIPA,openaid-IATI/OIPA,zimmerman-zimmerman/OIPA,zimmerman-zimmerman/OIPA,openaid-IATI/OIPA,zimmerman-zimmerman/OIPA