Add documentation links.

src/io/copy.rs

@@ -4,8 +4,10 @@ use futures::{Future, Poll};
 
 /// A future which will copy all data from a reader into a writer.
 ///
-/// Created by the `copy` function, this future will resolve to the number of
+/// Created by the [`copy`] function, this future will resolve to the number of
 /// bytes copied or an error if one happens.
+///
+/// [`copy`]: fn.copy.html
 pub struct Copy<R, W> {
     reader: R,
     read_done: bool,

src/io/flush.rs

@@ -6,7 +6,9 @@ use futures::{Poll, Future, Async};
 ///
 /// Resolves to the underlying I/O object once the flush operation is complete.
 ///
-/// Created by the `flush` function.
+/// Created by the [`flush`] function.
+///
+/// [`flush`]: fn.flush.html
 pub struct Flush<A> {
     a: Option<A>,
 }

src/io/read_exact.rs

@@ -6,7 +6,9 @@ use futures::{Poll, Future};
 /// A future which can be used to easily read exactly enough bytes to fill
 /// a buffer.
 ///
-/// Created by the `read_exact` function.
+/// Created by the [`read_exact`] function.
+///
+/// [`read_exact`]: fn.read_exact.html
 pub struct ReadExact<A, T> {
     state: State<A, T>,
 }

src/io/read_to_end.rs

@@ -6,7 +6,9 @@ use futures::{Poll, Future};
 /// A future which can be used to easily read the entire contents of a stream
 /// into a vector.
 ///
-/// Created by the `read_to_end` function.
+/// Created by the [`read_to_end`] function.
+///
+/// [`read_to_end`]: fn.read_to_end.html
 pub struct ReadToEnd<A> {
     state: State<A>,
 }

src/io/write_all.rs

@@ -5,7 +5,9 @@ use futures::{Poll, Future};
 
 /// A future used to write the entire contents of some data to a stream.
 ///
-/// This is created by the `write_all` top-level method.
+/// This is created by the [`write_all`] top-level method.
+///
+/// [`write_all`]: fn.write_all.html
 pub struct WriteAll<A, T> {
     state: State<A, T>,
 }