Tiny modification on admin.edit_article
1)Combined 'create_article' with 'save_article', replacing the former as a
'form'
2)Improve 'delete_reply', checking article_author in prior
3)Revised the admin module, moving some common functions into 'blog' and
remove the duplicated functions in 'admin' module
4)Revised 'article.html' of 'blog' module, add some functions
for the author of article, such as editing article and deleting replies.