temporarily regress to babel 5 for parity with sprockets-es6 gem

config/webpack.config.js

@@ -30,10 +30,7 @@ var config = {
       {
         test: /\.es6$/,
         exclude: /node_modules/,
-        loader: 'babel-loader',
-        query: {
-          presets: ['es2015']
-        }
+        loader: 'babel-loader'
       }
     ]
   },

package.json

@@ -7,9 +7,9 @@
     "eslint-report": "npm run eslint -- --format html --output-file ./eslint-report.html"
   },
   "dependencies": {
-    "babel-core": "^6.17.0",
-    "babel-loader": "^6.2.5",
-    "babel-preset-es2015": "^6.16.0",
+    "babel": "^5.8.38",
+    "babel-core": "^5.8.38",
+    "babel-loader": "^5.4.2",
     "stats-webpack-plugin": "^0.4.2",
     "webpack": "^1.13.2",
     "webpack-dev-server": "^1.16.2"