use vendor to manage dependancy

[leslie-wang]

Thanks for making the great project!

Seems like it requires some dependency. Probably go vendor can be used here to manage dependency. Thanks

$ go build
kmsg/nodeinfo.go:8:2: cannot find package "github.com/anacrolix/missinggo" in any of:
kmsg/compact_node_info.go:9:2: cannot find package "github.com/anacrolix/torrent/bencode" in any of:
main.go:16:2: cannot find package "github.com/anacrolix/torrent/iplist" in any of:
main.go:17:2: cannot find package "github.com/anacrolix/torrent/util" in any of:
token/server.go:11:2: cannot find package "github.com/bradfitz/iter" in any of:
rpc/bootstrap.go:13:2: cannot find package "github.com/tylertreat/BoomFilters" in any of: