Full-featured identify implementation

[ralexstokes]

We should reach feature-parity w/ the Go implementation of identify.

Some things missing:

• Sharing our view of our local addresses

[ShadowJonathan]

What do you mean with that? That we are able to send local multiaddresses to remote peers when in the identify stage, or we send our view of their peer address when in the identify stage?

[ralexstokes]

@ShadowJonathan resolving this TODO: https://github.com/libp2p/py-libp2p/blob/master/libp2p/identity/identify/protocol.py#L33

following the semantics here: https://github.com/libp2p/go-libp2p/blob/master/p2p/protocol/identify/id.go#L307-L309

[ShadowJonathan]

Should just be an easy fix if the client can grab the current connecting peer's multiaddr

[vipulnayyar]

Hey @pacrob , can you please assign me this issue?