build: upgrade babel to v7

Author: PeachScript

.babelrc

@@ -1,4 +1,3 @@
-const path = require('path');
 const webpackConfig = require('./webpack.config');
 
 delete webpackConfig.entry;

karma.conf.js

@@ -38,15 +38,15 @@
   },
   "homepage": "https://github.com/PeachScript/vue-infinite-loading",
   "devDependencies": {
+    "@babel/core": "^7.0.0",
+    "@babel/plugin-transform-runtime": "^7.0.0",
+    "@babel/preset-env": "^7.0.0",
+    "@babel/runtime": "^7.0.0",
     "@commitlint/cli": "^7.0.0",
     "@commitlint/config-conventional": "^7.0.1",
     "autoprefixer": "^9.1.5",
-    "babel-core": "^6.25.0",
-    "babel-loader": "^7.1.1",
-    "babel-plugin-istanbul": "^4.1.4",
-    "babel-plugin-transform-runtime": "^6.23.0",
-    "babel-preset-env": "^1.6.0",
-    "babel-preset-stage-2": "^6.24.1",
+    "babel-loader": "^8.0.2",
+    "babel-plugin-istanbul": "^5.0.1",
     "chai": "^3.5.0",
     "css-loader": "^0.28.4",
     "eslint": "^4.19.1",

package.json

@@ -34,7 +34,17 @@ module.exports = {
       {
         test: /\.js$/,
         include: [path.join(__dirname, './src'), path.join(__dirname, './test')],
-        loader: 'babel-loader'
+        loader: 'babel-loader',
+        options: {
+          presets: ['@babel/preset-env'],
+          plugins: ['@babel/plugin-transform-runtime'],
+          env: {
+            test: {
+              presets: [['@babel/preset-env', { useBuiltIns: 'usage' }]],
+              plugins: ['babel-plugin-istanbul']
+            }
+          }
+        }
       },
       {
         test: /\.vue$/,