fix a typo

package.json

@@ -1,6 +1,6 @@
 {
   "name": "dplayer",
-  "version": "1.17.3",
+  "version": "1.17.4",
   "description": "Wow, such a lovely HTML5 danmaku video player",
   "main": "dist/DPlayer.min.js",
   "style": "dist/DPlayer.min.css",

src/setting.js

@@ -1,6 +1,6 @@
 import utils from './utils';
 
-class SettingBox {
+class Setting {
     constructor (player) {
         this.player = player;
 
@@ -130,4 +130,4 @@ class SettingBox {
     }
 }
 
-module.exports = SettingBox;
+module.exports = Setting;