Replace prototype legacy with new code

We are using prototype_legacy_helper[1] in order to be able to use some Rails 2 only things in Rails 3. We need to update our code so as to not use any functions listed in [1] anymore. In theory it should work to replace code with code in the legacy helper.

[1] https://github.com/rails/prototype_legacy_helper/blob/master/lib/prototype_legacy_helper.rb
