Update node to 12

.travis.yml

@@ -7,7 +7,7 @@ jobs:
     - stage: test
       language: node_js
       node_js:
-        - 10
+        - 12
       name: "Lint src and check docs"
       script: npm run pre-commit
       if: type = pull_request
@@ -17,6 +17,8 @@ jobs:
       language: ruby
       rvm:
         - 2.4.1
+      before_install:
+        - nvm install 12
       script: ./deploy.sh
       if: branch = master AND type = push
       cache: bundler