Added a cartopy recipe.

Thanks. Sadly though, the test dependencies don't get built if there is no distribution available. For example, even if there is an owslib recipe and appropriate build distribution, I get the following:

```
$> conda build cartopy -t    
TEST START: cartopy-0.11.1-np18py27_0
Fetching package metadata: ...
Error: No packages found matching: owslib
```