Add REMSS OI SST product
Add the recent SST product from http://www.remss.com/measurements/sea-surface-temperature/.
More details are in: http://www.remss.com/measurements/sea-surface-temperature/oisst-description/
Let's go for the combined microwave-infrared data that is globally available from 2002 to the present.
The (already nc-deflated) daily fields are about 1MB each. So we're talking about 5 GB in total.
(cc: @rebecca-hummels)