use parallel bundler.

.travis.yml

@@ -1,11 +1,15 @@
 language: ruby
 
-bundler_args: '' # avoid travis-ci to set deployment mode by default
+bundler_args: '-j8' # avoid travis-ci to set deployment mode by default, and use parallel bundlerr
 
 before_script: bundle install
 
 script: bundle exec rake spec
 
+before_install:
+  - "echo 'gem: --no-ri --no-rdoc' > ~/.gemrc"
+  - gem install bundler --pre
+
 rvm: 2.0.0
 
 gemfile: