Add node 4.0, node 5.0 to Travis test targets

Author: wooorm

.travis.yml

@@ -3,6 +3,8 @@ node_js:
 - '0.10'
 - '0.11'
 - '0.12'
+- '4.0'
+- '5.0'
 - iojs
 sudo: false
 after_script: npm install codecov.io && cat ./coverage/lcov.info | codecov