Set up xvfb for Travis

.travis.yml

@@ -3,10 +3,12 @@ bundler_args: --without development
 rvm:
   - "1.9.3"
 services: postgresql
+before_install:
+  - "export DISPLAY=:99.0"
+  - "sh -e /etc/init.d/xvfb start"
 before_script:
   - cp config/database.travis.yml config/database.yml
   - psql -c 'create database open_food_web_test;' -U postgres
 script:
   - RAILS_ENV=test bundle exec rake db:migrate --trace
-  - bundle exec rake db:test:prepare
-  - bundle exec rspec spec
+  - export DISPLAY=:99.0 && bundle exec rake spec