reverted adding vue from externals, caused problems loading umd

Author: gmsa

dist/vue-grid-layout.common.js

@@ -1,8 +1,6 @@
 import Vue from 'vue'
 import App from './App.vue'
 
-Vue.config.productionTip = false
-
 new Vue({
   render: h => h(App)
 }).$mount('#app')

dist/vue-grid-layout.common.js.map

@@ -4,9 +4,6 @@ module.exports = {
             library: "VueGridLayout",
             libraryExport: 'default'
         },
-        externals: {
-            vue: 'vue'
-        },
     },
     css: {
         extract: false