travis: Add Node.js 11

RobLoach · web-flow · commit dbb903a6d2ce · 2019-01-14T13:14:00.000-05:00
diff --git a/.travis.yml b/.travis.yml
@@ -6,6 +6,7 @@ node_js:
   - "8"
   - "9"
   - "10"
+  - "11"
 
 after_success:
   - npm run coverage
