Add node 6 to Travis tests

pirelenito · pirelenito · commit 8ee316ef90dd · 2018-04-28T08:51:41.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,6 @@
 language: node_js
 node_js:
+  - "6.11.5"
   - "8"
   - "9"
 # send builds to the container-based infrastructure
