add linting to travis

Author: e-e-e

.travis.yml

@@ -1,11 +1,17 @@
 language: node_js
-node_js:
-  - 6
-  - 7
-  - 8
-  - 9
-  - 10
-script:
-  - npm run travis
-after_script:
-  - npm run report-coverage
+jobs:
+  include:
+    - stage: lint
+      node_js: 8
+      script: npm run lint
+    - stage: test
+      node_js:
+        - 6
+        - 7
+        - 8
+        - 9
+        - 10
+      script:
+        - npm run travis
+      after_script:
+        - npm run report-coverage