chore(babel): use env preset

Author: Awk34

Diff for: .babelrc

@@ -1,4 +1,10 @@
 {
-    "presets": ["es2015"],
-    "plugins": ["transform-class-properties"]
-}
+  "plugins": ["transform-class-properties"],
+  "presets": [
+    ["env", {
+      "targets": {
+        "node": "6.10"
+      }
+    }]
+  ]
+}

Diff for: package.json

@@ -39,10 +39,11 @@
   "dependencies": {
     "babel-core": "^6.20.0",
     "babel-eslint": "^7.1.0",
-    "babel-register": "^6.22.0",
     "babel-plugin-syntax-class-properties": "^6.13.0",
     "babel-plugin-syntax-flow": "^6.18.0",
     "babel-plugin-transform-flow-strip-types": "^6.18.0",
+    "babel-preset-env": "^1.7.0",
+    "babel-register": "^6.22.0",
     "bluebird": "^3.4.5",
     "chalk": "^2.1.0",
     "glob": "^7.0.5",