Update travis to latest stable nodeJS which is 8.

drewwestrick · jescalan · commit a94fb53ed12b · 2018-10-12T13:23:57.000-04:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,6 @@
 language: node_js
 sudo: false
 node_js:
-  - 6
+  - 8
 after_script:
   - npm run coveralls
