Award emoji supports retina displays

app/assets/stylesheets/pages/emojis.scss

@@ -1723,4 +1723,12 @@
   background-repeat: no-repeat;
   height: 20px;
   width: 20px;
+
+  @media only screen and (-Webkit-min-device-pixel-ratio: 1.5),
+  only screen and (-moz-min-device-pixel-ratio: 1.5),
+  only screen and (-o-min-device-pixel-ratio: 3/2),
+  only screen and (min-device-pixel-ratio: 1.5) {
+    background-image: image-url('emoji@2x.png');
+    background-size: 840px 820px;
+  }
 }