A different installation of ruby should be used. I use rbenv for that purpose.
# install your version of ruby
$ rbenv install 2.0.0-p247
# modify .ruby_version on current directory
$ rbenv local 2.0.0-p247
# proceed installing gems
$ gem install bundler
Disclamer: I am not a ruby person. This worked for me and if you are a ruby expert and see things to change in this answer, please, go ahead or comment!