Add a data directory (with a brief document outlining the data types). This...

Add a data directory (with a brief document outlining the data types). This repository omits the actual data files as they are too large, but the files may be made available elsewhere (and a note to that effect added to the README)

tests/data/README.md

+Notes
+=====
+
+To extract only the required variables from the full POLCOMS file, use the NetCDF Kitchen Sink toolkit as follows:
+
+% ncks -a -v time,pdepthD,ETWD,x1XD,lon,lat <infile> <outfile>