Update .travis.yml

- Ensure testing on LTS and latest node versions
- Minor speed improvements

.travis.yml

@@ -3,13 +3,20 @@ language: node_js
 node_js:
   - '0.10'
   - '0.12'
-  - 'iojs'
+  - '4.2'
+  - 'stable'
 
 before_install:
   - npm i npm@latest -g
 
+sudo: false
+
+git:
+  depth: 10
+
 script: make travis
 
+
 notifications:
   slack:
     secure: BiCHWsLTzlEd6MjRZY27BgmtCA3DmBFo5jcSsjSqmInbgla0lzDAA40xfIKTswIwK0pzuQdVaanl5Jy78wul0lfxpa5LLWX/bQmR1LGrygphC5tFG7GDM9Hdjatce5XEYVsSAUddNFEVQtMEUuUkSOiUll7kRq4LQtvAiIy1isk=