Adds ARIA labels to page elements

This includes calculator open/close button, navigation, profile, and
book's table of content.

templates/staticbook.html

@@ -59,7 +59,7 @@ $("#open_close_accordion a").click(function(){
 <section class="main-content">
   <div class="book-wrapper">
 
-    <section class="book-sidebar">
+    <section aria-label="Textbook Navigation" class="book-sidebar">
       <header id="open_close_accordion">
         <h2>Table of Contents</h2>
         <a href="#">close</a>