Make the node version explicit

Kuniwak · Kuniwak · commit 8bc9fa04b06f · 2015-09-20T18:08:23.000+09:00
diff --git a/.node-version b/.node-version
@@ -0,0 +1 @@
+v4.1.0
diff --git a/package.json b/package.json
@@ -28,6 +28,9 @@
   "bugs": {
     "url": "https://github.com/mixi-inc/JavaScriptTraining/issues"
   },
+  "engines": {
+    "node": "~4.1.0"
+  },
   "homepage": "https://github.com/mixi-inc/JavaScriptTraining",
   "devDependencies": {
     "body-parser": "1.14.0",
