Merge pull request #1203 from amber-smalltalk/travis-node4

.travis.yml: include node 4

.travis.yml

@@ -2,6 +2,7 @@ language: node_js
 node_js:
   - "0.10"
   - "0.12"
+  - "4"
 install:
   - npm install -g grunt-cli mocha
   - npm install