use node 6 image

sinclairzx81 · sinclairzx81 · commit ed952582d979 · 2019-02-06T18:46:45.000+13:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,5 @@
 language: node_js
 node_js:
-  - "10"
+  - "6"
 before_script:
   - npm install
