.travis.yml in bowser-0.3.0 vs .travis.yml in bowser-0.4.0

@@ -1,8 +1,9 @@
 language: ruby
 rvm:
   - 2.2.5
   - 2.3.1
+  - 2.4.1
   - jruby-9.0.5.0
   - jruby-9.1.1.0
 before_install:
   - wget https://s3.amazonaws.com/travis-phantomjs/phantomjs-2.0.0-ubuntu-12.04.tar.bz2
   - tar -xjf phantomjs-2.0.0-ubuntu-12.04.tar.bz2