* Refactor UDP SendDgram & RecvDgram
Get rid of unnamed structs in the favor of private structs with named fields
* Change the signature of UdpCodec::encode
Now it is:
```
fn encode(&mut self, msg: Self::Out, buf: &mut Vec<u8>) -> Result<SocketAddr, Self::Error>;
```
Closes https://github.com/tokio-rs/tokio/issues/79
* Fix compilation error from `mio` crate
* small doc cleanups in PollEvented
* small doc cleanups in IoToken
* improve crate level documentation
- Add links to the futures, mio and tokio-uds crates.
- Add links to various structs and types mentioned.
- use eprintln for error reporting in the example.
* improvements to the UdpSocket documentation
- Fixed links usage.
- Removed references to a no longer existing `Window` struct.
- Made notes about using functions in context of a future.
* documentation improvements to UdpFramed and UdpCodec
- Since HTTP uses TCP (QUIC aside) using it as an example in an UDP
protocol feels wrong.
- Make the note of tampering with the underlying streams more explicit.
* update reactor module level documentation
Adds an explanation of every public struct.
* expand Handle and Remote documentation
* expand net module documentation
Adds an explanation of every public struct and how they work together.
* update TcpListener documentation
Reorder the various option methods; get first then set.
Note about panicing added to poll_read.
* remove mention of none-existing future R
* improve documentation of TcpStream
* fix UdpSocket doc
This when wrong when merging various commits.
* Move to `std::net` as it's all purely UDP related
* Rename to `UdpCodec` and `UdpFramed` to give a consistent `Udp` prefix
* Add `RecvDgram`, rename `SendDGram` to `SendDgram`
* Touch up some style here and there
