Use matrix to split NodeJS and Ruby builds

.travis.yml

@@ -1,10 +1,11 @@
-language: node_js
+matrix:
+  include:
+    - language: node_js
       node_js:
         - "6"
 
       script:
         - npm run jsonlint
-  - jekyll build
 
       notifications:
         email:
@@ -17,3 +18,18 @@ deploy:
         api_key: "$NPM_KEY"
         on:
           branch: master
+
+    - language: ruby
+      rvm:
+        - 2.4.1
+
+      install:
+        - gem install jekyll
+
+      script:
+        - jekyll build
+
+      notifications:
+        email:
+          on_success: never
+          on_failure: change