Draft a new spec release

[piegamesde]

We've had quite a few interesting changes since 1.0.1, so a 1.1.0 might be a good idea. Some things that need to be addressed first though:

• The rendezvous server permissions is not 100% done and tested yet. Notably, I don't think we have implemented it in the rendezvous server and make use of it, so it's not really well tested. Protocol wise, I think a small question about error handling still needs to be resolved. Therefore, I'd like to exclude it from the release for now, although I don't know what the best way of doing so is.
• I'd like to mark the Dilation protocol as unstable for now (at the moment only Python implements it and it's CLI does not make use of it), to keep us the ability to fix issues that come up without getting into SemVer trouble.
• The maximum message size stuff for Transit would appreciate some additional love: I'd like the relay server be able to enforce message sizes too, and generally we need to implement this in clients.