Bump version # to release history link.

index.html

@@ -61,7 +61,7 @@
    <a href="libs/hana/index.html">Hana</a>,
    <a href="libs/metaparse/index.html">Metaparse</a>),
   as well as updates to many existing libraries. See
-  <a href="http://www.boost.org/users/history/version_1_60_0.html">Release
+  <a href="http://www.boost.org/users/history/version_1_61_0.html">Release
   History</a> for more information.</p>
 
   <h3>Getting Started</h3>