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, 227 deletions

diff --git a/examples/tinydb.rs b/examples/tinydb.rs
deleted file mode 100644
index 11298ed1..00000000
--- a/examples/tinydb.rs
+++ /dev/null
@@ -1,227 +0,0 @@
-//! A "tiny database" and accompanying protocol
-//!
-//! This example shows the usage of shared state amongst all connected clients,
-//! namely a database of key/value pairs. Each connected client can send a
-//! series of GET/SET commands to query the current value of a key or set the
-//! value of a key.
-//!
-//! This example has a simple protocol you can use to interact with the server.
-//! To run, first run this in one terminal window:
-//!
-//!     cargo run --example tinydb
-//!
-//! and next in another windows run:
-//!
-//!     cargo run --example connect 127.0.0.1:8080
-//!
-//! In the `connect` window you can type in commands where when you hit enter
-//! you'll get a response from the server for that command. An example session
-//! is:
-//!
-//!
-//!     $ cargo run --example connect 127.0.0.1:8080
-//!     GET foo
-//!     foo = bar
-//!     GET FOOBAR
-//!     error: no key FOOBAR
-//!     SET FOOBAR my awesome string
-//!     set FOOBAR = `my awesome string`, previous: None
-//!     SET foo tokio
-//!     set foo = `tokio`, previous: Some("bar")
-//!     GET foo
-//!     foo = tokio
-//!
-//! Namely you can issue two forms of commands:
-//!
-//! * `GET $key` - this will fetch the value of `$key` from the database and
-//!   return it. The server's database is initially populated with the key `foo`
-//!   set to the value `bar`
-//! * `SET $key $value` - this will set the value of `$key` to `$value`,
-//!   returning the previous value, if any.
-
-#![deny(warnings)]
-
-extern crate tokio;
-
-use std::collections::HashMap;
-use std::env;
-use std::io::BufReader;
-use std::net::SocketAddr;
-use std::sync::{Arc, Mutex};
-
-use tokio::io::{lines, write_all};
-use tokio::net::TcpListener;
-use tokio::prelude::*;
-
-/// The in-memory database shared amongst all clients.
-///
-/// This database will be shared via `Arc`, so to mutate the internal map we're
-/// going to use a `Mutex` for interior mutability.
-struct Database {
-    map: Mutex<HashMap<String, String>>,
-}
-
-/// Possible requests our clients can send us
-enum Request {
-    Get { key: String },
-    Set { key: String, value: String },
-}
-
-/// Responses to the `Request` commands above
-enum Response {
-    Value {
-        key: String,
-        value: String,
-    },
-    Set {
-        key: String,
-        value: String,
-        previous: Option<String>,
-    },
-    Error {
-        msg: String,
-    },
-}
-
-fn main() -> Result<(), Box<std::error::Error>> {
-    // Parse the address we're going to run this server on
-    // and set up our TCP listener to accept connections.
-    let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse::<SocketAddr>()?;
-    let listener = TcpListener::bind(&addr).map_err(|_| "failed to bind")?;
-    println!("Listening on: {}", addr);
-
-    // Create the shared state of this server that will be shared amongst all
-    // clients. We populate the initial database and then create the `Database`
-    // structure. Note the usage of `Arc` here which will be used to ensure that
-    // each independently spawned client will have a reference to the in-memory
-    // database.
-    let mut initial_db = HashMap::new();
-    initial_db.insert("foo".to_string(), "bar".to_string());
-    let db = Arc::new(Database {
-        map: Mutex::new(initial_db),
-    });
-
-    let done = listener
-        .incoming()
-        .map_err(|e| println!("error accepting socket; error = {:?}", e))
-        .for_each(move |socket| {
-            // As with many other small examples, the first thing we'll do is
-            // *split* this TCP stream into two separately owned halves. This'll
-            // allow us to work with the read and write halves independently.
-            let (reader, writer) = socket.split();
-
-            // Since our protocol is line-based we use `tokio_io`'s `lines` utility
-            // to convert our stream of bytes, `reader`, into a `Stream` of lines.
-            let lines = lines(BufReader::new(reader));
-
-            // Here's where the meat of the processing in this server happens. First
-            // we see a clone of the database being created, which is creating a
-            // new reference for this connected client to use. Also note the `move`
-            // keyword on the closure here which moves ownership of the reference
-            // into the closure, which we'll need for spawning the client below.
-            //
-            // The `map` function here means that we'll run some code for all
-            // requests (lines) we receive from the client. The actual handling here
-            // is pretty simple, first we parse the request and if it's valid we
-            // generate a response based on the values in the database.
-            let db = db.clone();
-            let responses = lines.map(move |line| {
-                let request = match Request::parse(&line) {
-                    Ok(req) => req,
-                    Err(e) => return Response::Error { msg: e },
-                };
-
-                let mut db = db.map.lock().unwrap();
-                match request {
-                    Request::Get { key } => match db.get(&key) {
-                        Some(value) => Response::Value {
-                            key,
-                            value: value.clone(),
-                        },
-                        None => Response::Error {
-                            msg: format!("no key {}", key),
-                        },
-                    },
-                    Request::Set { key, value } => {
-                        let previous = db.insert(key.clone(), value.clone());
-                        Response::Set {
-                            key,
-                            value,
-                            previous,
-                        }
-                    }
-                }
-            });
-
-            // At this point `responses` is a stream of `Response` types which we
-            // now want to write back out to the client. To do that we use
-            // `Stream::fold` to perform a loop here, serializing each response and
-            // then writing it out to the client.
-            let writes = responses.fold(writer, |writer, response| {
-                let mut response = response.serialize();
-                response.push('\n');
-                write_all(writer, response.into_bytes()).map(|(w, _)| w)
-            });
-
-            // Like with other small servers, we'll `spawn` this client to ensure it
-            // runs concurrently with all other clients, for now ignoring any errors
-            // that we see.
-            let msg = writes.then(move |_| Ok(()));
-
-            tokio::spawn(msg)
-        });
-
-    tokio::run(done);
-    Ok(())
-}
-
-impl Request {
-    fn parse(input: &str) -> Result<Request, String> {
-        let mut parts = input.splitn(3, " ");
-        match parts.next() {
-            Some("GET") => {
-                let key = match parts.next() {
-                    Some(key) => key,
-                    None => return Err(format!("GET must be followed by a key")),
-                };
-                if parts.next().is_some() {
-                    return Err(format!("GET's key must not be followed by anything"));
-                }
-                Ok(Request::Get {
-                    key: key.to_string(),
-                })
-            }
-            Some("SET") => {
-                let key = match parts.next() {
-                    Some(key) => key,
-                    None => return Err(format!("SET must be followed by a key")),
-                };
-                let value = match parts.next() {
-                    Some(value) => value,
-                    None => return Err(format!("SET needs a value")),
-                };
-                Ok(Request::Set {
-                    key: key.to_string(),
-                    value: value.to_string(),
-                })
-            }
-            Some(cmd) => Err(format!("unknown command: {}", cmd)),
-            None => Err(format!("empty input")),
-        }
-    }
-}
-
-impl Response {
-    fn serialize(&self) -> String {
-        match *self {
-            Response::Value { ref key, ref value } => format!("{} = {}", key, value),
-            Response::Set {
-                ref key,
-                ref value,
-                ref previous,
-            } => format!("set {} = `{}`, previous: {:?}", key, value, previous),
-            Response::Error { ref msg } => format!("error: {}", msg),
-        }
-    }
-}