Add node version for CircleCI

circle.yml

@@ -4,7 +4,10 @@ machine:
     - mongodb
   environment:
     MONGO_URI: mongodb://127.0.0.1/crowi_test
+  node:
+      version: 4.6.2
+  post:
+    - npm install -g npm@3
 notify:
   webhooks:
     - url: https://webhooks.gitter.im/e/5a035388e3274b621d20
-