Implement server library.

[aatxe]

I've been waiting for IO to settle for a while now, but I think it's in a good position to work on a server component. It should likely be somewhat based on the new std::net design.

[aatxe]

So, I think #16 has mostly settled on a design, which means the next step is definitely to implement a server library. I'm still not entirely sure what the scope should be though. Should it just cover server-to-server protocols? Should it provide an event loop with mio or something of the sort?

[fahlmant]

I'm currently learning Rust and I'm interested in helping.

[aatxe]

It's been a long time since I had an active interest in writing a new IRCd from scratch, and I could never find the time to work on it. As such, I've officially limited the scope of this library to what it already was in practice: client support and general protocol stuff.

[VictorKoenders]

I'd be interested in making an IRC server, is it still outside of the scope of this project? If this turns out to be a separate project, it would be great to have the proto folder be its own package