Hide horizontal scroolbar in navigation pane

Fixes gh-48

Author: philwebb

src/main/css/toc.css

@@ -66,7 +66,7 @@ body.toc-left #doc {
 body.fixed-toc #toc {
   position: fixed;
   top: 0;
-  overflow-x: scroll;
+  overflow-x: hidden;
   height: 100%;
 }