support attachment, and basic port of renren share and facebook on attachment
use plural form of attachment (attachments)
Merge branch 'remove-too-verbose-debug-log' into attachment-support
a better structure of Message.parsed.attachments
attachment support for RenrenBlog
add video, link, and make picture better for facebook
set default value of Message.parsed.attachments to []
Merge branch 'attachment-support'

This merge includes:
 * Attachments on snstype.Message
 * Basic attachments support for facebook and renren