readme: update imports in examples (#20)

Author: Dominic

README.md

@@ -21,8 +21,8 @@ keyword. The stream block must return `()`.
 ```rust
 use async_stream::stream;
 
-use futures_util::pin_mut;
-use futures_util::stream::StreamExt;
+use futures::pin_mut;
+use futures::stream::StreamExt;
 
 #[tokio::main]
 async fn main() {
@@ -45,9 +45,9 @@ Streams may be returned by using `impl Stream<Item = T>`:
 ```rust
 use async_stream::stream;
 
-use futures_core::stream::Stream;
-use futures_util::pin_mut;
-use futures_util::stream::StreamExt;
+use futures::stream::Stream;
+use futures::pin_mut;
+use futures::stream::StreamExt;
 
 fn zero_to_three() -> impl Stream<Item = u32> {
     stream! {
@@ -73,9 +73,9 @@ Streams may be implemented in terms of other streams:
 ```rust
 use async_stream::stream;
 
-use futures_core::stream::Stream;
-use futures_util::pin_mut;
-use futures_util::stream::StreamExt;
+use futures::stream::Stream;
+use futures::pin_mut;
+use futures::stream::StreamExt;
 
 fn zero_to_three() -> impl Stream<Item = u32> {
     stream! {
@@ -115,7 +115,7 @@ of the returned stream is `Result` with `Ok` being the value yielded and
 use tokio::net::{TcpListener, TcpStream};
 
 use async_stream::try_stream;
-use futures_core::stream::Stream;
+use futures::stream::Stream;
 
 use std::io;
 use std::net::SocketAddr;
@@ -159,7 +159,7 @@ If large `stream!` blocks are used, the caller will be required to add
 
 A `stream!` macro may only contain up to 64 macro invocations.
 
-[`Stream`]: https://docs.rs/futures-core/*/futures_core/stream/trait.Stream.html
+[`stream`]: https://docs.rs/futures-core/*/futures_core/stream/trait.Stream.html
 [`proc-macro-hack`]: https://github.com/dtolnay/proc-macro-hack/
 
 ## License