removed leo's email, added TT

public/index.php

@@ -143,7 +143,7 @@
         <hr>
         <br>
         <p style="color:grey">
-        If you have any suggestions for improvement, please give feedback via <a href="mailto:leonard.koellenberger@kit.edu">email</a>.
+        If you have any suggestions for improvement, please give feedback via <a href="mailto:thuemmler@kit.edu">email</a>.
         </p>
         <br>
         <br>