.travis.yml in slack-ruby-bot-server-0.6.1 vs .travis.yml in slack-ruby-bot-server-0.7.0

- old
+ new

@@ -14,12 +14,19 @@
     - rvm: 2.3.1
       env: DATABASE_ADAPTER=mongoid
       services:
         - mongodb
 
+addons:
+  firefox: 54.0
+
 before_install:
-  - "export DISPLAY=:99.0"
-  - "sh -e /etc/init.d/xvfb start"
+  - 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
 
 script:
   - bundle exec rake
   - BUNDLE_GEMFILE=Gemfile && cd sample_apps/sample_app_$DATABASE_ADAPTER && bundle && bundle exec rake