feat(examples): add grpc-web example (#710)

Creates a server using tonic-web and a client that uses a regular
`hyper::Client` and issues a regular HTTP/1.1 request.

tonic-web/README.md

@@ -1,46 +1,38 @@
 # tonic-web
 
-Enables tonic servers to handle requests from `grpc-web` clients directly, without the need of an
-external proxy. 
+Enables tonic servers to handle requests from `grpc-web` clients directly,
+without the need of an external proxy. 
 
 ## Getting Started
 
- ```toml
- [dependencies]
- tonic_web = "0.1"
- ```
+```toml
+[dependencies]
+tonic_web = "0.1"
+```
 
- ## Enabling tonic services
+## Enabling tonic services
 
- The easiest way to get started, is to call the function with your tonic service and allow the tonic 
- server to accept HTTP/1.1 requests:
+The easiest way to get started, is to call the function with your tonic service
+and allow the tonic server to accept HTTP/1.1 requests:
 
- ```rust
- #[tokio::main]
- async fn main() -> Result<(), Box<dyn std::error::Error>> {
-     let addr = "[::1]:50051".parse().unwrap();
-     let greeter = GreeterServer::new(MyGreeter::default());
+```rust
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let addr = "[::1]:50051".parse().unwrap();
+    let greeter = GreeterServer::new(MyGreeter::default());
 
-     Server::builder()
-        .accept_http1(true)
-        .add_service(tonic_web::enable(greeter))
-        .serve(addr)
-        .await?;
+    Server::builder()
+       .accept_http1(true)
+       .add_service(tonic_web::enable(greeter))
+       .serve(addr)
+       .await?;
 
-    Ok(())
- }
- ```
+   Ok(())
+}
+```
 
 ## Examples
 
-[tonic-web-demo][1]: React+Typescript app that talking to a tonic-web enabled service using HTTP/1 or TLS.
+See [the examples folder][example] for a server and client example.
 
-[conduit][2]: An (in progress) implementation of the [realworld][3] demo in Tonic+Dart+Flutter. This app shows how
-the same client implementation can talk to the same tonic-web enabled server using both `grpc` and `grpc-web` protocols
-just by swapping the channel implementation. 
-
-When the client is compiled for desktop, ios or android, a  grpc `ClientChannel` implementation is used.
-When compiled for the web, a `GrpcWebClientChannel.xhr` implementation is used instead.``
-[1]: https://github.com/alce/tonic-web-demo
-[2]: https://github.com/alce/conduit
-[3]: https://github.com/gothinkster/realworld
+[example]: https://github.com/hyperium/tonic/tree/master/examples/src/tower