mechanize：Mechanize#visited_page

>> require 'mechanize'
=> true
>> agent = Mechanize.new
=> #<Mechanize:0xb749737c ...
>> agent.visited_page("http://www.foo.org/")
=> nil
>> agent.visited_page("http://www.google.com/")
=> nil
>> agent.get("http://www.google.com/")
=> #<Mechanize::Page
 {url #<URI::HTTP:0xb7485c80 URL:http://www.google.co.jp/>}
  ...
>> agent.visited_page("http://www.google.com/")
=> #<Mechanize::Page
 {url #<URI::HTTP:0xb7485c80 URL:http://www.google.co.jp/>}
  ...