Fix encoding for geoip provider

Geoip module return ISO-8859-1 encoded strings. Special characters are broken if not converted to utf8 before applying any transformation (like https://github.com/willdurand/Geocoder/blob/master/src/Geocoder/Result/AbstractResult.php#L64)
Merge pull request #227 from EmmanuelVella/patch-1

Fix encoding for geoip provider