Add JSON tags for ResultInfo in ZonesResponse and AvailableZoneRatePlansResponse (#260)
Add JSON tags for ResultInfo in ZonesResponse and AvailableZoneRatePlansResponse (#260)

Pagination doesn't work as I always get `0` on all the Println below:

```
popts := cloudflare.PaginationOptions{
	PerPage: 1000,
}
zoneRes, err := cf.ListZonesContext(context.Background(), cloudflare.ReqOption(cloudflare.WithPagination(popts)))
if err != nil {
	panic(err)
}

log.Println(zoneRes.Total)
log.Println(zoneRes.TotalPages)
log.Println(zoneRes.ResultInfo.Count)
log.Println(zoneRes.ResultInfo.Total)
log.Println(zoneRes.ResultInfo.Page)
log.Println(zoneRes.ResultInfo.TotalPages)

log.Fatalln(len(zoneRes.Result))
```

I saw the http response was correct here ( https://github.com/cloudflare/cloudflare-go/blob/master/zone.go#L351 ) but json.Unmarshal was not setting correct values. After applying the tags, it worked.
cloudflare/cloudflare-go,cloudflare/cloudflare-go