Fix: Adjust travis configuration

Author: markusguenther

.travis.yml

@@ -10,8 +10,10 @@ script: 'echo "No test specified";'
 php:
   - '7.1'
 before_install:
+  - nvm install 8.11.0 && nvm use
   - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.9.4
   - export PATH="$HOME/.yarn/bin:$PATH"
+  - yarn install
 after_success:
   - yarn semantic-release
 branches: