Nicer timestamps with momentjs

This dependency may be a little heavy for our current use case, but we can
roll with it for now and find something slimmer if it turns out yagni.

Closes #77
Closes #40

test/index.html

@@ -56,6 +56,7 @@
         <ul class='volley'>
             <li class='message'>
             {{ message }}
+            <span class='timestamp'>{{ timestamp }}</span>
             </li>
         </ul>
         {{#attachments}}

test/views/message_view_test.js

@@ -18,6 +18,18 @@ describe('MessageView', function() {
     assert.match(view.$el.html(), /goodbye world/);
   });
 
+  it('should have a nice timestamp', function() {
+    var view = new Whisper.MessageView({model: message});
+    message.set({'timestamp': new Date().getTime() - 5000});
+    assert.match(view.$el.html(), /seconds ago/);
+
+    message.set({'timestamp': new Date().getTime() - 60000});
+    assert.match(view.$el.html(), /minute ago/);
+
+    message.set({'timestamp': new Date().getTime() - 3600000});
+    assert.match(view.$el.html(), /hour ago/);
+  });
+
   it('should go away when the model is destroyed', function() {
     var view = new Whisper.MessageView({model: message});
     var div = $('<div>').append(view.$el);