v0.7.0

• Use the NAT status events to trigger changes in AutoRelay instead of polling. This should result in faster AutoRelay setup.
• Update to a unified (i.e., unified client+server) and improved AutoNAT service.
• Avoid running any services on the AutoNAT dialer (no identify, ping, etc.).
• Fix a regression in 0.6 where the in-memory peerstore wasn't getting properly closed on shutdown.
• Emit events on the event bus when the local addresses change.
• New options for AutoNAT:
  • WithReachability can force libp2p to start as "reachable" or "unreachable" and not try to autodetect reachability.
  • EnableNATService can be passed to make this node act as an AutoNAT server.