.travis.yml in byebug-1.4.1 vs .travis.yml in byebug-1.4.2

@@ -1,3 +1,8 @@
+before_install: gem install bundler
 before_script: rake compile
 rvm:
 - 2.0.0
+- ruby-head
+matrix:
+  allow_failures:
+  - rvm: ruby-head