add delAttribute method to parser
add clean_article_tags method, clean classes, ids and name attribute from article tags
add gizmodo tests
Add cookie handeling exemple in known issues
updated README
no need for OSX setup info
pep8
return image even if local_image is None
move assert_top_image to image test file
add test for known_image_css, known_image_name, opengraph_tag
known image css work at element level
Merge pull request #38 from grangier/imageextractor

known image css work at element level