Changed lots of peer use, and changed the peerstore to ensure
there is only ever one peer in use.

Fixed #174

![](http://m.memegen.com/77n7dk.jpg)

Now, all peers should be retrieved from the Peerstore, which will
construct the peers accordingly. This ensures there's only one peer
object per peer (opposite would be bad: things get out sync)

cc @whyrusleeping

object plumbing commands

Some fixes to bitswap + dht