Added method to set ids from within the page

Added a method to the embed javascript to set the blog ID and post ID from
within the body of a webpage, and have that used to be the ids that are loaded
by the javascript.  This would allow someone to set the IDs in a standalone
page hosted elsewhere on the web and have it behave as a blog-app blog that is
pseudo-self-hosted, and could be wrapped in a custom webpage and theme.
Made permalink generation recognize blogapp_id setup

If you're using blogapp_id/blogapp_post javascript variables, the
permalinks will now be formatted to set the URL to be a page with
the URI of post ID.  You can capture this with rewrites or some
other programmatic method and convert them into setting blogapp_id
and blogapp_post on the requested page which will result in
returning the proper post.
Merge pull request #2 from baldown/standalone

Enabling a embed-based standalone blog-app backed blog