use node 10 image

sinclairzx81 · sinclairzx81 · commit ea24c04e31db · 2019-02-06T18:48:43.000+13:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,5 @@
 language: node_js
 node_js:
-  - "6"
+  - "10"
 before_script:
   - npm install
