Change Server to contain a Vec of (ip, port) pairs to allow repeat listening

Expose Server::many for creating a Server that will listen on many (ip, port)
pairs.

Handler still receives a simple Iterator of (Request, Response) pairs.

This is a breaking change since it changes the representation of Listener,
but Handler and Server::http are unchanged in their API.

Fixes #7

src/lib.rs

@@ -9,6 +9,8 @@ extern crate url;
 #[phase(plugin,link)] extern crate log;
 #[cfg(test)] extern crate test;
 extern crate "unsafe-any" as uany;
+extern crate "move-acceptor" as macceptor;
+extern crate intertwine;
 
 pub use std::io::net::ip::{SocketAddr, IpAddr, Ipv4Addr, Ipv6Addr, Port};
 pub use mimewrapper::mime;