Susburrows/add region support amwg set10

Example global plot:
![set10_ann_trefht_ncep](https://cloud.githubusercontent.com/assets/6811403/5514284/0b1a3bd4-87df-11e4-82d6-2361575fe595.png)

"Southern extratropics" version:
![settesting_ann_trefht_ncep](https://cloud.githubusercontent.com/assets/6811403/5514283/033f3dd8-87df-11e4-8381-b89b5005db42.png)