test: add v4 and v5 to travis

Author: Myles Borins

.travis.yml

@@ -4,5 +4,7 @@ node_js:
   - "0.10"
   - "0.12"
   - "iojs"
+  - "4"
+  - "5"
 before_install:
   - npm install -g npm@~1.4.6