Write spec for 'hello' protocol

[whyrusleeping]

Description

We need to document the 'hello' protocol in the spec. This should go in the 'network-protocols.md' document for now, and be sufficient for someone to implement the protocol fully.

Where to begin

Pull down the latest specs here: https://github.com/filecoin-project/specs and add the changes to the bottom of the 'network-protocols.md' document.

Try to follow the format that the other protocols documented there follow, but if you feel like improving on the model, please do (and make a note of the divergence in the PR, then i'll adjust the other docs to match).

Submit your changes as a PR to the specs repo, and we will move forward from there

[whyrusleeping]

cc @ZenGround0

[whyrusleeping]

@ZenGround0 any progress here?

[acruikshank]

@whyrusleeping Why is this an issue in filecoin-project/go-filecoin and not filecoin-project/specs?

[whyrusleeping]

@acruikshank so that devs will see the issues. @phritz and I discussed this and decided it would be easiest to have these issues here so they aren't hidden away in a repo that most devs never look at.

[whyrusleeping]

PR: filecoin-project/specs#153