Modification history:
July 3,2017 -
 populated Readme with information about hindcast procedure
July 6,2017 -
 checked out the frozen tag GEOS-S2S-2_1,
 manually moved the scripts that differ from yuri-S2S-2_1_UNSTABLE to tag_xxxx files,
 replaced them by the ones from yuri-S2S-2_1_UNSTABLE
August 10, 2017 -
 checked out the yuri-S2S-2_1_UNSTABLE
 updated the scripts
 asked Yury to add new ones :forecast vs hindcast (emissions, RC), subX vs seasonal (diag_table, MOM_OUtput, duration,postprocessing, perturbation)
 commit? create new tag?
 change the link geos-s2s to point to a new build
