.travis.yml :: test node v5 and stop testing just "iojs"

"iojs" stopped after v3.x so there's no need for yet another v3 test.

Author: mimetnet

.travis.yml

@@ -19,7 +19,7 @@ node_js:
   - '0.10'
   - '0.12'
   - '4'
+  - '5'
   - 'iojs-v1.0.0'
   - 'iojs-v2.0.0'
   - 'iojs-v3.0.0'
-  - 'iojs'