GitLab

Sending a protocol version is nice. However, this "disconnect if our versions
are different" logic makes the version entirely useless (because we can't change
it).

Really, each indevidual protocol is versioned so let's just leave it at that. If
we make a breaking change that requires a protocol bump, we can do that and
then switch on the other side's version. However, we'll have to wait for the
entire network to upgrade for that to work.