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, 58 deletions

diff --git a/examples/hello_world.rs b/examples/hello_world.rs
deleted file mode 100644
index c8276269..00000000
--- a/examples/hello_world.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-//! Hello world server.
-//!
-//! A simple client that opens a TCP stream, writes "hello world\n", and closes
-//! the connection.
-//!
-//! You can test this out by running:
-//!
-//!     ncat -l 6142
-//!
-//! And then in another terminal run:
-//!
-//!     cargo run --example hello_world
-
-#![deny(warnings)]
-
-extern crate tokio;
-
-use tokio::io;
-use tokio::net::TcpStream;
-use tokio::prelude::*;
-
-pub fn main() -> Result<(), Box<std::error::Error>> {
-    let addr = "127.0.0.1:6142".parse()?;
-
-    // Open a TCP stream to the socket address.
-    //
-    // Note that this is the Tokio TcpStream, which is fully async.
-    let client = TcpStream::connect(&addr)
-        .and_then(|stream| {
-            println!("created stream");
-            io::write_all(stream, "hello world\n").then(|result| {
-                println!("wrote to stream; success={:?}", result.is_ok());
-                Ok(())
-            })
-        })
-        .map_err(|err| {
-            // All tasks must have an `Error` type of `()`. This forces error
-            // handling and helps avoid silencing failures.
-            //
-            // In our example, we are only going to log the error to STDOUT.
-            println!("connection error = {:?}", err);
-        });
-
-    // Start the Tokio runtime.
-    //
-    // The Tokio is a pre-configured "out of the box" runtime for building
-    // asynchronous applications. It includes both a reactor and a task
-    // scheduler. This means applications are multithreaded by default.
-    //
-    // This function blocks until the runtime reaches an idle state. Idle is
-    // defined as all spawned tasks have completed and all I/O resources (TCP
-    // sockets in our case) have been dropped.
-    println!("About to create the stream and write to it...");
-    tokio::run(client);
-    println!("Stream has been created and written to.");
-
-    Ok(())
-}