[chore] Use babel-preset-env instead of babel-preset-es2015

Author: Aditya Vohra

Diff for: .babelrc

@@ -1,5 +1,9 @@
 {
-  "presets": ["es2015", "stage-2", "react"],
+  "presets": [
+    "env",
+    "react",
+    "stage-2"
+  ],
   "plugins": [
     "add-module-exports"
   ]

Diff for: package.json

@@ -27,7 +27,7 @@
     "babel-eslint": "^8.0.1",
     "babel-loader": "^7.1.2",
     "babel-plugin-add-module-exports": "^0.2.1",
-    "babel-preset-es2015": "^6.24.1",
+    "babel-preset-env": "^1.6.0",
     "babel-preset-react": "^6.24.1",
     "babel-preset-stage-2": "^6.24.1",
     "coveralls": "^2.13.1",