chore: Fix examples not working with `cargo run` (#998)

* chore: Fix examples not working with `cargo run`

## Motivation

PR #991 moved the `tokio` crate to its own subdirectory, but did not
move the `examples` directory into `tokio/examples`. While attempting to
use the examples for testing another change, I noticed that #991 had
broken the ability to use `cargo run`, as the examples were no longer
considered part of a crate that cargo was aware of:

```
tokio on master [$] via 🦀v1.33.0 at ☸️ aks-eliza-dev
➜  cargo run --example chat
error: no example target named `chat`

Did you mean `echo`?
```

## Solution

This branch moves the examples into the `tokio` directory, so cargo is
now once again aware of them:

```
tokio on eliza/fix-examples [$] via 🦀v1.33.0 at ☸️ aks-eliza-dev
➜  cargo run --example chat
   Compiling tokio-executor v0.1.7 (/Users/eliza/Code/tokio/tokio-executor)
   Compiling tokio-reactor v0.1.9
   Compiling tokio-threadpool v0.1.13
   Compiling tokio-current-thread v0.1.6
   Compiling tokio-timer v0.2.10
   Compiling tokio-uds v0.2.5
   Compiling tokio-udp v0.1.3
   Compiling tokio-tcp v0.1.3
   Compiling tokio-fs v0.1.6
   Compiling tokio v0.1.18 (/Users/eliza/Code/tokio/tokio)
    Finished dev [unoptimized + debuginfo] target(s) in 7.04s
     Running `target/debug/examples/chat`
server running on localhost:6142
```

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

1 files changed, 0 insertions, 65 deletions

diff --git a/examples/udp-codec.rs b/examples/udp-codec.rs
deleted file mode 100644
index 3657d8cc..00000000
--- a/examples/udp-codec.rs
+++ /dev/null
@@ -1,65 +0,0 @@
-//! This example leverages `BytesCodec` to create a UDP client and server which
-//! speak a custom protocol.
-//!
-//! Here we're using the codec from tokio-io to convert a UDP socket to a stream of
-//! client messages. These messages are then processed and returned back as a
-//! new message with a new destination. Overall, we then use this to construct a
-//! "ping pong" pair where two sockets are sending messages back and forth.
-
-#![deny(warnings)]
-
-extern crate env_logger;
-extern crate tokio;
-extern crate tokio_codec;
-extern crate tokio_io;
-
-use std::net::SocketAddr;
-
-use tokio::net::{UdpFramed, UdpSocket};
-use tokio::prelude::*;
-use tokio_codec::BytesCodec;
-
-fn main() -> Result<(), Box<std::error::Error>> {
-    let _ = env_logger::init();
-
-    let addr: SocketAddr = "127.0.0.1:0".parse()?;
-
-    // Bind both our sockets and then figure out what ports we got.
-    let a = UdpSocket::bind(&addr)?;
-    let b = UdpSocket::bind(&addr)?;
-    let b_addr = b.local_addr()?;
-
-    // We're parsing each socket with the `BytesCodec` included in `tokio_io`, and then we
-    // `split` each codec into the sink/stream halves.
-    let (a_sink, a_stream) = UdpFramed::new(a, BytesCodec::new()).split();
-    let (b_sink, b_stream) = UdpFramed::new(b, BytesCodec::new()).split();
-
-    // Start off by sending a ping from a to b, afterwards we just print out
-    // what they send us and continually send pings
-    // let pings = stream::iter((0..5).map(Ok));
-    let a = a_sink.send(("PING".into(), b_addr)).and_then(|a_sink| {
-        let mut i = 0;
-        let a_stream = a_stream.take(4).map(move |(msg, addr)| {
-            i += 1;
-            println!("[a] recv: {}", String::from_utf8_lossy(&msg));
-            (format!("PING {}", i).into(), addr)
-        });
-        a_sink.send_all(a_stream)
-    });
-
-    // The second client we have will receive the pings from `a` and then send
-    // back pongs.
-    let b_stream = b_stream.map(|(msg, addr)| {
-        println!("[b] recv: {}", String::from_utf8_lossy(&msg));
-        ("PONG".into(), addr)
-    });
-    let b = b_sink.send_all(b_stream);
-
-    // Spawn the sender of pongs and then wait for our pinger to finish.
-    tokio::run({
-        b.join(a)
-            .map(|_| ())
-            .map_err(|e| println!("error = {:?}", e))
-    });
-    Ok(())
-}