Test Node v9

Author: jakezatecky

.travis.yml

@@ -3,6 +3,7 @@ node_js:
   - '6'
   - '7'
   - '8'
+  - '9'
 before_script:
   # Remove ./node_modules/.bin from PATH so node-which doesn't replace Unix which and cause RVM to barf. See https://github.com/travis-ci/travis-ci/issues/5092
   - PATH=${PATH//:\.\/node_modules\/\.bin/}