Update localhost address to empty string

elo_tracker/app.py

@@ -502,11 +502,11 @@ class EloTracker:
   <script>
     var app = Elm.EloTracker.init({
         node: document.body,
-        flag: { baseUrl: "http://127.0.0.1:5000" }
+        flag: { baseUrl: "" }
     });
   </script>
 </html>
-""".strip(),
+""".strip(), # TODO: Make base URL more explicit
                 mimetype="text/html",
             )