Magnetsuri

Read torrent will also support reading information from magnet uri.

Also, when feross/magnet-uri#2 gets merged and published the resulting information will be more, and will match the one resulting from `parse-torrent`.

This assumes https://github.com/mafintosh/read-torrent/pull/3. I made a separate PR because you might or might not implement this. 

@mafintosh, but here's why I think you should:

- *"read and parse a torrent from a resource"*
Magnets URI are also a valid resource for torrent information.

- This code gets simplified:
``` js
if (/^magnet:/.test(filename)) return ontorrent(filename);

readTorrent(filename, function(err, torrent) {
	if (err) return console.error(err);
	ontorrent(torrent);
});
```


If you need a `rebase` let me know. 
(You can also merge this and close https://github.com/mafintosh/read-torrent/pull/3., since this one contains both commits)