This installs the alexa library which provides a method top_list which can
give you the top N items from alexa's top_sites.

For example:

    >>> import alexa
    >>> alexa.top_list(20)
    [('1', 'google.com'), ('2', 'facebook.com'), ('3', 'yahoo.com'), ('4',
    'youtube.com'), ('5', 'live.com'), ('6', 'wikipedia.org'), ('7',
    'blogger.com'), ('8', 'msn.com'), ('9', 'baidu.com'), ('10',
    'yahoo.co.jp'), ('11', 'myspace.com'), ('12', 'google.co.in'), ('13',
    'twitter.com'), ('14', 'google.de'), ('15', 'qq.com'), ('16',
    'microsoft.com'), ('17', 'rapidshare.com'), ('18', 'wordpress.com'),
    ('19', 'google.fr'), ('20', 'google.co.uk')]