build: Setup build process to use ES6

Author: bitIO

.travis.yml

@@ -9,8 +9,11 @@ node_js:
   - '9'
   - '8'
   - '6'
+script:
+  - npm run test
+  - npm run build
 after_success:
   - npm run travis-deploy-once "npm run semantic-release"
 branches:
   except:
-    - /^v\d+\.\d+\.\d+$/
+    - /^v\d+\.\d+\.\d+$/