Merge pull request nestjs#639 from DanielRuf/chore/use-npm-ci

chore: use npm ci instead of npm install (travis)

Author: kamilmysliwiec

.travis.yml

@@ -7,8 +7,10 @@ addons:
 before_script:
      - export DISPLAY=:99.0
      - sh -e /etc/init.d/xvfb start
+before_install:
+     - npm i -g npm@latest
 install:
-     - npm install
+     - npm ci
      - gulp build
 script:
       - npm test