Fix Build Failed in Travis CI:

This commit set trusty as image to use and revert this commit changes

Add xvfb as service: 3c31460f2f
Remove failing script: d5cb60b19c

.travis.yml

@@ -1,12 +1,12 @@
+dist: trusty
 language: node_js
 node_js:
  - "8"
-services:
- - xvfb
 before_script:
  - yarn danger ci
  - npm install grunt-cli -g
  - "export DISPLAY=:99.0"
+ - "sh -e /etc/init.d/xvfb start"
  - sleep 5
 script:
 - grunt