Doc warning about CSV files with headers on HDFS

Change-Id: I8ca0a12ed09a7a067302b376558998b069c2ef78
Reviewed-on: http://fulliautomatix.ics.uci.edu:8443/233
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ian Maxon <imaxon@uci.edu>
1 file changed