Updated xvfb usage to example in Travis docs

Author: Simon Hofmann

.travis.yml

@@ -45,13 +45,15 @@ before_install:
 before_script:
   # Start xvfb
   - if [[ $TRAVIS_OS_NAME == "linux" ]]; then export DISPLAY=:99.0; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" ]]; then sh -e /etc/init.d/xvfb start; fi
+  - if [[ $TRAVIS_OS_NAME == "linux" ]]; then sleep 3; fi
 
 install: true
 
 script:
   - npm run patch && npm i
   - if [[ $TRAVIS_OS_NAME = "windows" ]]; then npm run build:release:win; else npm run build:release; fi
-  - if [[ $TRAVIS_OS_NAME == "linux" ]]; then xvfb-run npm test; else npm test; fi
+  - npm test
 
 before_deploy:
   - echo "//registry.npmjs.org/:_authToken=\${NPM_TOKEN}" >> $HOME/.npmrc 2> /dev/null