Teams now have country codes

I was building a d3 visualization and felt as though it would be useful for teams to have a country code column.  This comes in handy when you are using other APIs to get country flags, for example.  

Included in this pull request is the migration and a rake task that can be run as follows: 

```bash 
 rake team:get_all_country_codes
```
Cheers, 
Matt