Merge pull request #1 from ruby/enable-travis

To use ruby-head for Ruby 2.5.0dev.

Author: hsbt

.travis.yml

@@ -1,5 +1,5 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.5.0
-before_install: gem install bundler -v 1.14.3
+  - ruby-head
+before_install: gem install bundler