(magnet links support) async info dictionary handling; infodictionary from peers if we have no one

fetching info dictionary from peers. Now we can load torrent data only if we have infoHash (magnet links support)

uses this changes
https://github.com/feross/parse-torrent/pull/1
https://github.com/mafintosh/peer-wire-protocol/pull/4
https://github.com/mafintosh/peer-wire-swarm/pull/5


strict mode; jshint fixes