add pub sub client implementation with examples (#22)

* add pub sub client implementation with examples

* replace subscribed_channels list Vec with HashSet to avoid duplicates

* update Subscriber to use async-stream instead of manual Stream impl

* revert update to error handling server.rs, as #21 handles it

* remove uneeded recursion limit extension

examples/pub.rs

@@ -1,4 +1,31 @@
+//! Publish to a redis channel example.
+//!
+//! A simple client that connects to a mini-redis server, and
+//! publishes a message on `foo` channel
+//!
+//! You can test this out by running:
+//!
+//!     cargo run --bin server
+//!
+//! Then in another terminal run:
+//!
+//!     cargo run --example sub
+//!
+//! And then in another terminal run:
+//!
+//!     cargo run --example pub
+
+#![warn(rust_2018_idioms)]
+
+use mini_redis::{client, Result};
+
 #[tokio::main]
-async fn main() {
-    unimplemented!();
+async fn main() -> Result<()> {
+    // Open a connection to the mini-redis address.
+    let mut client = client::connect("127.0.0.1:6379").await?;
+
+    // publish message `bar` on channel foo
+    client.publish("foo", "bar".into()).await?;
+
+    Ok(())
 }

examples/sub.rs

@@ -1,6 +1,37 @@
-/// Subscribe to a redis channel
+//! Subscribe to a redis channel example.
+//!
+//! A simple client that connects to a mini-redis server, subscribes to "foo" and "bar" channels
+//! and awaits messages published on those channels
+//!
+//! You can test this out by running:
+//!
+//!     cargo run --bin server
+//!
+//! Then in another terminal run:
+//!
+//!     cargo run --example sub
+//!
+//! And then in another terminal run:
+//!
+//!     cargo run --example pub
+
+#![warn(rust_2018_idioms)]
+
+use mini_redis::{client, Result};
 
 #[tokio::main]
-async fn main() {
-    unimplemented!();
+pub async fn main() -> Result<()> {
+    // Open a connection to the mini-redis address.
+    let client = client::connect("127.0.0.1:6379").await?;
+
+
+    // subscribe to channel foo
+    let mut subscriber = client.subscribe(vec!["foo".into()]).await?;
+
+    // await messages on channel foo
+    let msg = subscriber.next_message().await? ;
+    println!("got message from the channel: {}; message = {:?}", msg.channel, msg.content);
+
+
+    Ok(())
 }