Upgraded to the latest version of 6to5

package.json

@@ -34,9 +34,9 @@
     "keycharm": "^0.2.0"
   },
   "devDependencies": {
-    "6to5": "^2.12.2",
-    "6to5-loader": "^2.0.0",
-    "6to5ify": "^4.0.0",
+    "6to5": "^3.5.3",
+    "6to5-loader": "^3.0.0",
+    "6to5ify": "^4.1.0",
     "clean-css": "latest",
     "gulp": "^3.8.5",
     "gulp-concat": "^2.2.0",