JRFC 36 - SND -- reversed + pathed DNS

I really, really dislike the backwards-to-paths nature of dns. It's not like [Unix](https://en.wikipedia.org/wiki/Unix#History) and other hierarchical file systems didn't exist in [1983](https://en.wikipedia.org/wiki/Domain_Name_System#History). So let's [reverse](https://en.wikipedia.org/wiki/Reverse_domain_name_notation) it, and use [paths](https://en.wikipedia.org/wiki/Unix_File_System).

``` sh
# dns
releases.lists.refs.ipfs.io

# snd
ipfs.io/refs/lists/releases
cat /snd/ipfs.io/refs/lists/releases
curl fs://snd/ipfs.io/refs/lists/releases
```

For all this, we need:
- [ ] an snd resolver that uses dns
- [ ] an HTTP server that serves snd lookups
- [ ] a FUSE filesystem that mounts snd
- [ ] the `fs://` standard and handler

This will help with "the DNS web".