Update travis.yml to node_js 4 from iojs-v2.3.4 (#1)

Author: shum

.travis.yml

@@ -1,15 +1,16 @@
 language: node_js
 node_js:
-  - 'iojs-v2.3.4'
+  - 4
 before_install:
   - npm install -g npm@3
   - npm config set loglevel error
   - npm config -g list -l
   - npm --version
 script: npm run-script ci
-cache:
-  directories:
-    - node_modules
+# Disable cache to force travis to use node_js ver 4
+#cache:
+#  directories:
+#    - node_modules
 # Post build notifications to the Integrations Flowdock
 notifications:
   flowdock: e3dc17bc8a2c1b3412abe3e5747f8291