fix(Travis): fix travis yaml file

Author: st0ffern

.travis.yml

@@ -1,14 +1,19 @@
+
 language: node_js
+cache:
+  directories:
+    - ~/.npm
 notifications:
   email: false
 node_js:
+  - '9'
   - '8'
+install:
+  - npm install
 before_script:
   - npm prune
-  - npm i -g eslint
-  - npm i -D eslint-plugin-react
 after_success:
   - npm run semantic-release
 branches:
   except:
-    - /^v\d+\.\d+\.\d+$/
+    - /^v\d+\.\d+\.\d+$/