.travis.yml in slack-ruby-bot-server-0.11.1 vs .travis.yml in slack-ruby-bot-server-0.12.0

@@ -2,27 +2,29 @@
 
 cache: bundler
 
 matrix:
   include:
-    - rvm: 2.3.1
+    - rvm: 2.6.2
       script:
         - bundle exec danger
-    - rvm: 2.3.1
+      services:
+        - xvfb
+    - rvm: 2.6.2
       env: DATABASE_ADAPTER=activerecord
       services:
+        - xvfb
         - postgresql
-    - rvm: 2.3.1
+    - rvm: 2.6.2
       env: DATABASE_ADAPTER=mongoid
       services:
+        - xvfb
         - mongodb
 
 addons:
   firefox: 54.0
 
 before_install:
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start
   - wget https://github.com/mozilla/geckodriver/releases/download/v0.18.0/geckodriver-v0.18.0-linux64.tar.gz
   - mkdir geckodriver
   - tar -xzf geckodriver-v0.18.0-linux64.tar.gz -C geckodriver
   - export PATH=$PATH:$PWD/geckodriver