If your using Rails 4 then Client Side validation is outdated. You can check here
http://railscasts.com/episodes/263-client-side-validations?view=comments
and also if you go to the github page
https://github.com/bcardarella/client_side_validations
you can see that it says its no longer maintained.
Alternatively you can try using the CSV gem from this branch, by replacing the CSV line in your Gemfile by this
gem 'client_side_validations', github: "bcardarella/client_side_validations", :branch => "4-0-beta"
Not sure even if this will work though. Since its outdated.
Or you can check this gem out,
https://github.com/kalkov/rails4_client_side_validations
Its just a modified version of Client Side Validations