Support iteration over the GeoIP city database

[larsyencken]

It'd be awesome to be able to iterate through the city database. It seems a ruby client has implemented this feature:

https://github.com/cjheath/geoip/blob/master/lib/geoip.rb#L332

[tiwilliam]

Took a while to understand what you meant, the link had been updated and pointed to another function. For future readers, the function can be seen at the link below.

https://github.com/cjheath/geoip/blob/e2f064c209ee94ddbc6fc056d7f8eecdcb565b47/lib/geoip.rb#L391