chore: fix travis (#336)

.travis.yml

@@ -1,10 +1,10 @@
 language: node_js
 node_js:
-  - "0.12"
   - "4.0"
   - "6.0"
 
 before_install:
+  - npm update npm -g
   - npm install -g grunt-cli
 
 #travis build  speed up