add note re: SSLv2 to event webhook

source/API_Reference/Webhooks/event.html

@@ -22,6 +22,10 @@ <h2>Setup</h2>
 {% endcodeblock %}
 </blockquote>
 
+<blockquote><span class="label label-warning">Warning</span> If you wish
+to receive encrypted posts, we require that your callback URL support
+SSL v2.</blockquote>
+
 <p>To setup the even
 <h2>Requests</h2>
 <p>You have the option to receive a <strong>HTTP POST</strong> request for each event or to receive a batch of multiple events in one request after a very short delay. These POSTs will be sent to the URL you have defined in the Event Notification app options. </p>
@@ -376,4 +380,4 @@ <h2>Troubleshooting</h2>
 <p>Ensure that your web server is returning a 200 response to our servers. Any other response type will result in our server retrying a POST until we receive a 200 response or the maximum time has expired. All events are retried at increasing intervals for up to three days after the event occurs. Make sure you are not blocking our IPs that are trying to POST to your server. Our IPs change often since we constantly add more machines. Also, you can try a test POST yourself from a terminal by running the following command. This will give you the full response your server is returning including the HTTP headers.</p>
 {% codeblock lang:bash %}
 curl -i -d 'email=test@gmail.com&arg2=2&arg1=1&category=testing&event=processed'
-{% endcodeblock %}
+{% endcodeblock %}