Enhance Kaminari support of negative paddings

page_scope_methods.rb

module Kaminari
  module PageScopeMethods
    def padding(num)
      @_padding = num
      new_offset_value = offset_value + num.to_i
      if new_offset_value < 0
        limit([limit_value + new_offset_value, 0].max).offset(0)
      else
        offset(new_offset_value)
      end
    end
  end
end