Required changes for Rails 4

Hi, I made the required changes to use the Client Side Validations with Rails 4. All tests are passing and I didn't see problems in my project (using Mongoid and SimpleForm).

I'm sending this pull request against the branch '3-2-stable', but I'm sure you are going to create a new branch for the new version (4.0.0).

Thank you for your project, and if you need more changes/info, please, tell me.