Fix for Kaminari strange window implementation. Works with Kaminari 0.13

kaminari.rb

# Fixes https://github.com/amatsuda/kaminari/issues/133
# put into /initializers/kaminari.rb

module Kaminari
  module Helpers
    class Paginator < Tag
      class PageProxy
        def inside_window?
          if @options[:current_page] <= @options[:window]
            @page <= (@options[:window] * 2) + 1
          elsif (@options[:num_pages] - @options[:current_page].number) < @options[:window]
            @page >= (@options[:num_pages] - (@options[:window] * 2))
          else
            (@options[:current_page] - @page).abs <= @options[:window]
          end
        end
      end
    end
  end
end