chore(travis): test also in Node 9

gr2m · gr2m · commit e1aca12ec234 · 2017-11-29T15:26:16.000-08:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,6 @@
 language: node_js
 node_js:
+  - "9"
   - "8"
   - "6"
   - "4"
