Make devise 3 on Rails 4 work with signed_form.

gistfile1.rb

class ParameterSanitizer < Devise::ParameterSanitizer
  def for(kind)
    @params.fetch @resource_name, {}
  end
end

class ApplicationController < ActionController::Base
  include SignedForm::ActionController::PermitSignedParams

  protected

  def devise_parameter_sanitizer
    ParameterSanitizer.new resource_name, params
  end
end