RSS description message can now address single or multi-author setup

"each of your post" flows better when trimmed to "each post".

This change also frees it up for when blog is multi-author as it
is no longer confined to addressing one person, but for all posts
as a complete blog whole.
Update Google Webmasters link about rel=canonical
Merge pull request #106 from randomecho/copyedit-seo-settings

RSS description message can now address single or multi-author setup