Pass custom emoji data directly to <Preview />

<Preview /> calls getData() itself which will fail for custom emojis because there is no universally available data source for custom emojis. To work around this, we pass the custom emoji data (which <Picker /> received via the `custom` prop) directly to <Preview />.

src/components/picker.js

@@ -152,7 +152,8 @@ export default class Picker extends React.Component {
 
   handleEmojiOver(emoji) {
     var { preview } = this.refs
-    preview.setState({ emoji: emoji })
+    const emojiData = CUSTOM_CATEGORY.emojis.find(customEmoji => customEmoji.id === emoji.id)
+    preview.setState({ emoji: Object.assign(emoji, emojiData) })
     clearTimeout(this.leaveTimeout)
   }