Get country (code) for an ip address

What we want to have:
When #12 (closed) is solved, we have our current IP address. In the next step we need to get our current coutry (code). Then we can tell it menshen to get nearest vpn gateways.

v3 uses https://api.black.riseup.net:9001/json which returns a sorted list of gateways.

The big topic here is: how to do the mapping ip address <=> country (code). Add a menshen endpoint, ask a public api, or add a local geoip database to the client?