Use newest released rubygems and bundler

This would fix build failures on 1.9

Author: amatsuda

.travis.yml

@@ -3,6 +3,10 @@ language: ruby
 sudo: false
 cache: bundler
 
+before_install:
+  - gem update --system
+  - gem install bundler
+
 rvm:
   - 1.9
   - 2.0