Atom web feed not include deleted entries and contributor list

When using activity stream to generate web feed, it is almost same no matter type is atom_1.0 or rss_1.0.
The mainly issues are as following.

• Not including deleted entries in ATOM feed.
• Raise exception when list contributors' information.
• The create and update timestamp is always same.

The exceptions about listing contributors can be refered the post in forum (https://forum.xwiki.org/t/how-to-create-atom-web-feed/489/5)