Update travis node test versions.

- Bump 4.0 to 4.2.
- Remove iojs.

Author: davidlehn

.travis.yml

@@ -2,9 +2,8 @@ language: node_js
 node_js:
   - "0.10"
   - "0.12"
-  - "4.0"
+  - "4.2"
   - "node"
-  - "iojs"
 sudo: false
 # download test suite and run tests... submodule? meta testing project with
 # all of the reference implementations?