Convert new library info into a template

[ci skip]

index.html

@@ -55,9 +55,15 @@
 
   <h3>Changes in this release</h3>
 
-  <p>The release includes ??? new libraries
-  (),
-  as well as updates to many existing libraries. See
+  {{#unreleased_lib_count}}
+  <p>The release includes {{unreleased_lib_count}} new libraries
+  ({{#unreleased_libs}}{{#index}}, {{/index}}<a href="{{link}}">{{name}}</a>{{/unreleased_libs}})
+  as well as updates to many existing libraries.
+  {{/unreleased_lib_count}}
+  {{^unreleased_lib_count}}
+  <p>The release includes updates to many existing libraries.
+  {{/unreleased_lib_count}}
+  See
   <a href="http://www.boost.org/users/history/version_1_63_0.html">Release
   History</a> for more information.</p>