This Commit changes the relationship between Conn and Swarm.
After this, Conn is significantly more autonomous, and follows
an interface.

From here, it will be very easy to make the MultiConn (that
handles multiple Conns per peer).

@whyrusleeping `make vendor` or travis fails

(that wasn't mine :p)

Otherwise don't have the peer's target address.

Important bugfix. Otherwise bitswap cannot message peers
the node has not connected to yet :(

fix IPFS_DEBUG (was set after SetupLogging)

Version handshake