ci: test on all lts node version on linux (#364)

Author: evilebottnawi

.travis.yml

@@ -5,15 +5,17 @@ jobs:
   include:
     - stage: Lint
       env: SCRIPT=lint
-      node_js: 'stable'
+      node_js: 6
     - &test
       stage: Test
       env: SCRIPT=test
-      node_js: 'stable'
+      node_js: 6
     - <<: *test
-      node_js: 'lts/*'
+      node_js: 8
     - <<: *test
-      node_js: 6
+      node_js: 10
+    - <<: *test
+      node_js: 11
 
 script: npm run $SCRIPT