Allow tests to run in older versions of node

Author: sergiocruz

package.json

@@ -5,15 +5,24 @@
   "private": true,
   "scripts": {
     "start": "browser-sync start --server ./src --files ./src",
-    "test": "mocha test/*.spec.js",
+    "test": "mocha --compilers js:babel-register test/*.spec.js",
     "deploy:github-pages": "git subtree push --prefix src origin gh-pages"
   },
   "author": "Sergio Cruz <[email protected]>",
   "license": "MIT",
   "devDependencies": {
+    "babel-preset-es2015": "^6.18.0",
+    "babel-register": "^6.18.0",
     "browser-sync": "^2.14.0",
     "chai": "^3.5.0",
     "jsdom": "^9.4.1",
     "mocha": "^3.0.1"
+  },
+  "engines": {
+    "node": ">=4.6",
+    "npm": ">=2.15"
+  },
+  "babel": {
+    "presets": ["es2015"]
   }
 }