prevent npm install on travis

Author: Khartir

.travis.yml

@@ -5,6 +5,8 @@ cache:
   yarn: true
   directories:
     - node_modules
-script: yarn && yarn bootstrap && yarn ci
+install:
+  - yarn
+script: yarn bootstrap && yarn ci
 after_success:
   - bash <(curl -s https://codecov.io/bash) -e TRAVIS_NODE_VERSION