[#14] Add General Law Information

Fixes #14 

Kinda tempted to put `identity_card_number` in `GeneralLaw` too.
If you use `form_for(@user_signup, :as => :user_signup` in the form, all the controller needs to have is something like 


    UserController.class_eval do

      before_filter :setup_signup_user, :only => [:signin]

      def setup_signup_user
          @user_signup = User.new
          @user_signup.build_general_law
      end

      private

      def user_params(key = :user)
          params[key].slice(:name,
                            :email,
                            :password,
                            :identity_card_number,
                            :password_confirmation,
                            :general_law_attributes,
                            :terms)
      end

    end