Add user_data.js

Script will be used to obtain data from server for D3 consumption.

spotifyvis/templates/spotifyvis/user_data.html

@@ -16,5 +16,6 @@
         <![endif]-->
         <h1>Logged in as {{ id }}</h1>
         <h2>Display name {{ user_name }}</h2>
+        <script src="{% static 'spotifyvis/scripts/user_data.js' %}"></script>
     </body>
 </html>