libp2p DHT work

[whyrusleeping]

Since we will be needing to use the DHT for several parts of filecoin, we should put some work into fixing up a few things. This issue will serve to track the different improvements we will be helping out with. I'll add new issues here as they come up

• Help review and get dht pipelining merged
• Investigate dht put issue

[whyrusleeping]

Also, anyone feeling like cleaning up the DHT code in general should feel free to do so.

[whyrusleeping]

This put value issue is worse than I thought initially (libp2p/go-libp2p-kad-dht#139). If anyone wants to take a stab at it very soon, please do. Caution: It might get complicated, so be prepared, you will learn a lot about libp2p.

[laser]

@whyrusleeping I just split this out into two independent stories:

DHT Pipelining: https://app.zenhub.com/workspace/o/filecoin-project/go-filecoin/issues/433

DHT Put: https://app.zenhub.com/workspace/o/filecoin-project/go-filecoin/issues/437