.travis.yml in rutl-0.6.0 vs .travis.yml in rutl-0.8.0

@@ -1,7 +1,8 @@
 sudo: required
 addons:
   chrome: stable
+  firefox: latest
 language: ruby
 rvm:
   - 2.3.1
 before_install: gem install bundler -v 1.13.6
 script: bundle exec rspec