OSMID can be bigger than an int

[mpitt]

Hi and first of all thanks for the exporter!

I upgraded to v0.0.13 because I was facing #49, unfortunately the new geocoding method is also coming up short:

level=info msg="Looking up: Rovereto, IT"
level=fatal msg="failed to resolve location:json: cannot unmarshal number 3409185846 into Go struct field SearchResult.osm_id of type int"

It looks like the osm_id field can be a number bigger than what the int type can represent. I don't know what the maximum value can be, in my case an int64 is enough, but I guess it could even be ignored completely since it doesn't seem to be used anywhere.