abstract out dht routing table

[jbenet]

We need to:

• remove levels stuff for now
• abstract out dht routing table
• implement coral levels as another impl

[whyrusleeping]

im unsure how an interface for that would feel... we would need something like: "GetPeers" and then "GetMorePeers"

[jbenet]

Perhaps, the right thing to do is something like this:

type DHT interface {
  FindPeersNear(context.Context, u.Key) <-chan *peer.Peer
}

Because we can keep the goroutine fetching more and more close peers (with some rate-limit) until it's cancelled.

Rate limiting can happen in the context (WithValue).

[whyrusleeping]

alright, i like that.

[whyrusleeping]

closing, not an issue for now, may be in the future, can reopen later if necessary (or just start a new issue)