Fix typo (#159)

diff --git a/README.md b/README.md
index 359b93a..f7ed8be 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,7 @@
   [`DelegatingStreamSink`][DelegatingStreamSink].
 
 * The [`FutureGroup`][FutureGroup] class makes it easy to wait until a group of
-  features that may change over time completes.
+  futures that may change over time completes.
 
 * The [`LazyStream`][LazyStream] class allows a stream to be initialized lazily
   when `.listen()` is first called.