Remove obsolete version of node, add new versions

Author: peterolson

.travis.yml

@@ -1,13 +1,11 @@
 language: node_js
 node_js:
+  - "9"
+  - "8"
+  - "7"
   - "6"
   - "5"
   - "4"
-  - "iojs"
-  - "0.12"
-  - "0.11"
-  - "0.10"
-
 script:
  - npm test
  - cat ./coverage/lcov.info | ./node_modules/.bin/coveralls