fix build

package.json

@@ -8,6 +8,7 @@
     "babel-eslint": "^7.1.1",
     "babel-plugin-yo-yoify": "^0.3.3",
     "babel-polyfill": "^6.22.0",
+    "babel-plugin-transform-object-assign": "^6.22.0",
     "babel-preset-es2015": "^6.24.0",
     "babelify": "^7.3.0",
     "brace": "^0.8.0",
@@ -104,7 +105,7 @@
               "wrapAwait": true
             }
           }],
-          ["yo-yoify"]
+          ["yo-yoify"], ["transform-object-assign"]
         ],
         "presets": ["es2015"]
       }],