use correct ES2015 syntax (#31)

buhrmi · Guillaume Chau · commit f5c9b764a0e7 · 2017-08-02T13:07:53.000+02:00
diff --git a/index.js b/index.js
@@ -1,3 +1,3 @@
-export default from './dist/vue-virtual-scroller'
+export {default} from './dist/vue-virtual-scroller'
 export * from './dist/vue-virtual-scroller'
 import './dist/vue-virtual-scroller.css'
