Upgrade emoji support and switch to apple emoji

Use emojijs for replacing unicode with image tags for display. We were
already using it to replace colons with unicode. Additionally it has
a companion data repo that is kept up to date with images from all
the common image sets.

// FREEBIE

js/views/message_view.js

@@ -125,20 +125,10 @@
 
             this.renderControl();
 
-            twemoji.parse(this.el, {
-              attributes: function(icon, variant) {
-                var colon = emoji_util.get_colon_from_unicode(icon);
-                if (colon) {
-                  return {title: ":" + colon + ":"};
-                } else {
-                  return {};
-                }
-              },
-              base: '/images/twemoji/',
-              size: 16
-            });
-
             var body = this.$('.body');
+
+            emoji_util.parse(body);
+
             if (body.length > 0) {
                 var escaped = body.html();
                 body.html(escaped.replace(/\n/g, '<br>').replace(URL_REGEX, "$1<a href='$2' target='_blank'>$2</a>"));