Add title text for emoji in messages.

Fixes #250

// FREEBIE

background.html

@@ -363,6 +363,7 @@
   <script type='text/javascript' src='js/chromium.js'></script>
   <script type='text/javascript' src='js/conversation_controller.js'></script>
   <script type='text/javascript' src='js/panel_controller.js'></script>
+  <script type='text/javascript' src='js/emoji_util.js'></script>
 
   <script type='text/javascript' src='js/views/whisper_view.js'></script>
   <script type='text/javascript' src='js/views/debug_log_view.js'></script>

js/emoji_util.js

@@ -0,0 +1,32 @@
+/*
+ * vim: ts=4:sw=4:expandtab
+ */
+
+;(function() {
+    'use strict';
+
+    window.emoji_util = window.emoji_util || {};
+
+    // Map from single unicode emoji strings to "colon" strings
+    var unicode_emoji_map;
+    var initialized = false;
+
+    function initialize() {
+      if (initialized) {
+        return;
+      }
+      initialized = true;
+      unicode_emoji_map = {};
+      $.each(emoji.data, function(_, data) {
+        if (data[0] && data[0][0] && data[3] && data[3].length > 0) {
+          unicode_emoji_map[data[0][0]] = data[3][0];
+        }
+      });
+    }
+
+    window.emoji_util.get_colon_from_unicode = function(emoji_string) {
+      initialize();
+      return unicode_emoji_map[emoji_string];
+    };
+
+})();

js/views/message_view.js

@@ -87,7 +87,19 @@
 
             this.renderControl();
 
-            twemoji.parse(this.el, { base: '/images/twemoji/', size: 16 });
+            twemoji.parse(this.el, {
+              attributes: function(icon, variant) {
+                var colon = emoji_util.get_colon_from_unicode(icon);
+                console.log("colon: ", colon);
+                if (colon) {
+                  return {title: ":" + colon + ":"};
+                } else {
+                  return {};
+                }
+              },
+              base: '/images/twemoji/',
+              size: 16
+            });
 
             var content = this.$('.content');
             var escaped = content.html();