Reorganize the entire crate:

Renamed APIs

* Loop => reactor::Core
* LoopHandle => reactor::Handle
* LoopPin => reactor::Pinned
* TcpStream => net::TcpStream
* TcpListener => net::TcpListener
* UdpSocket => net::UdpSocket
* Sender => channel::Sender
* Receiver => channel::Receiver
* Timeout => reactor::Timeout
* ReadinessStream => reactor::PollEvented
* All `LoopHandle` methods to construct objects are now free functions on the
  associated types, e.g. `LoopHandle::tcp_listen` is now `TcpListener::bind`
* All APIs taking a `Handle` now take a `Handle` as the last argument
* All future-returning APIs now return concrete types instead of trait objects

Added APIs

* io::Io trait -- Read + Write + ability to poll

Removed without replacement:

* AddSource
* AddTimeout
* IoToken
* TimeoutToken

Closes #3
Closes #6

src/net/mod.rs

@@ -0,0 +1,11 @@
+//! TCP/UDP bindings for `tokio-core`
+//!
+//! This module contains the TCP/UDP networking types, similar to the standard
+//! library, which can be used to implement networking protocols.
+
+mod tcp;
+mod udp;
+
+pub use self::tcp::{TcpStream, TcpStreamNew};
+pub use self::tcp::{TcpListener, TcpListenerNew, Incoming};
+pub use self::udp::{UdpSocket, UdpSocketNew};