ci: update travis config

Author: DJTB

.travis.yml

@@ -1,12 +1,22 @@
 language: node_js
+
+cache:
+  directories:
+    - ~/.npm
+
 notifications:
   email: false
-node_js:
-  - 'node'
+
+node_js: '8'
+
 script: npm start validate
-after_success:
-  - npm install -g codecov semantic-release
-  - codecov
-  - semantic-release pre && npm publish && semantic-release post
+
+after_success: npx codecov
+
+deploy:
+  provider: script
+  skip_cleanup: true
+  script: npx semantic-release
+
 branches:
   except: /^v\d+\.\d+\.\d+$/