Susburrows/add region support amwg set8

These zonal mean seasonal cycle plots really need axis labels be added for clarity!

Global plot:
![set8_ann_trefht_ncep](https://cloud.githubusercontent.com/assets/6811403/5514218/d78dfb88-87da-11e4-8440-8ba384493639.png)

"Southern extratropics" version:
![settesting_ann_trefht_ncep](https://cloud.githubusercontent.com/assets/6811403/5514219/f684a640-87da-11e4-9cdc-1187aff27802.png)