Tweak prompt for tooting other's horn; #7

Try to steer people towards addressing others directly. So far the
couple I've seen are addressed in the third person.

www/%username/horn/index.html

@@ -27,7 +27,8 @@ <h2>Toot their horn!</h2>
             What have you done today that's awesome? Don't be shy!<br />
             Anyone who gave you money last week will see this on their Horn.
             {% else %}
-            Why do you appreciate {{ participant.username }}?
+            Thank {{ participant.username }} for something!<br />
+            This will be public on their Horn (without your name attached).
             {% end %}
             </span>
             <button id="toot-button" type="submit">Toot</button>