Use yl2chen/cidranger for prefix matching

[jpillora]

Swap the slice-based (O(n)) prefix matching out for https://github.com/yl2chen/cidranger (Thanks @yl2chen!)

Edit: Also investigate https://github.com/Kentik/patricia

[yl2chen]

enjoy!

[anacrolix]

Is https://github.com/anacrolix/torrent/blob/master/iplist/iplist.go of any interest? Probably not as efficient but I use it heavily.