Add display of timestamps for when we receive the message

It doesn't look like we can know from the Message in Kafka when it was actually
received by Kafka, so this will be enough to give us some semblence of time

FIxes #20

src/ratpack/handlebars/topic-watch.html.hbs

@@ -36,6 +36,7 @@
 {{=<% %>=}}
 <script id="message-display-template" type="text/x-handlebars-template">
     <div id="{{message_id}}" class="list-group-item message-container">
+        <div class="message-timestamp">{{timestamp}}</div>
         <code>{{topic}}:{{partition}}</code>
         <span class="offset">(offset: {{offset}})</span>
         <pre class="pre-scrollable message-raw">{{raw}}</pre>
@@ -47,6 +48,7 @@
 </script>
 <%={{ }}=%>
 
+<script src="/js/moment.min.js"></script>
 <script src="/js/ws.js"></script>
 <script type="text/javascript">
     watchTopic("{{name}}");

src/ratpack/public/css/offtopic.css

@@ -22,3 +22,7 @@ body {
     font-family: monospace;
     font-size: 0.7em;
 }
+
+.message-timestamp {
+    float: right;
+}

src/ratpack/public/js/ws.js

@@ -23,7 +23,8 @@ function watchTopic(name) {
                     partition: data.partition,
                     offset: data.offset,
                     raw: data.raw,
-                    b64: data.b64
+                    b64: data.b64,
+                    timestamp: moment(data.tstamp, 'x').format('MMM Do YYYY, H:mm:ss')
                 }));
 
                 $("#" + el_id).click(function(ev) {