Retrieve audio feature data from frontend

Added user_secret field to User. Set up a basic JavaScript function for
querying audio feature data from the frontend.

spotifyvis/templates/spotifyvis/user_data.html

@@ -16,11 +16,10 @@
             <p class="browsehappy">You are using an <strong>outdated</strong> browser. Please <a href="#">upgrade your browser</a> to improve your experience.</p>
         <![endif]-->
         <p>Logged in as {{ id }}</p>
-        <h2>Display name {{ user_name }}</h2>
-				<ul>
-					{% for genre_name, genre_count in genre_dict.items %}
-						<li>{{ genre_name }} - {{ genre_count }}</li>
-					{% endfor %}
-        </ul>
+        <script src="{% static "spotifyvis/scripts/user_data.js" %}"></script>
+        <script>
+            sessionStorage.setItem('user_secret', "{{ user_secret }}");
+            getAudioFeatureData('instrumentalness', sessionStorage.getItem('user_secret'));
+        </script>
     </body>
 </html>