Singular 'library' when appropriate

Mustache is really terrible for this kind of thing.

index.html

@@ -56,7 +56,9 @@
   <h3>Changes in this release</h3>
 
   {{#unreleased_lib_count}}
-  <p>The release includes {{unreleased_lib_count}} new libraries
+  <p>The release includes {{unreleased_lib_count}} new
+  {{#unreleased_library_plural}}libraries{{/unreleased_library_plural}}
+  {{^unreleased_library_plural}}library{{/unreleased_library_plural}}
   ({{#unreleased_libs}}{{#index}}, {{/index}}<a href="{{link}}">{{name}}</a>{{/unreleased_libs}})
   as well as updates to many existing libraries.
   {{/unreleased_lib_count}}