support global panel if no iso code given

Fixes #11. Just added a webapp2 route that didn't require an iso code. Ranges and aggregates are supported too. This has been deployed.

`http://wip.forma-api.appspot.com/api/counts?range=2008-01-01,2008-02-03`

```json
{
   "country":"Comoros",
   "data":[
      {
         "id":"COM",
         "series":[
            [
               "2008-01-01",
               1
            ],
            [
               "2008-01-17",
               3
            ],
            [
               "2008-02-02",
               2
            ]
         ],
         "name":"Comoros",
         "level":0
      },
      {
         "id":"GAB",
         "series":[
            [
               "2008-01-17",
               1
            ]
         ],
         "name":"Gabon",
         "level":0
      },
      {
         "id":"GUY",
         "series":[
            [
               "2008-01-01",
               8
            ],
            [
               "2008-01-17",
               9
            ],
            [
               "2008-02-02",
               18
            ]
         ],
         "name":"Guyana",
         "level":0
      }
   ]
}
```