Add blog posts to snapshot tests

[kjaymiller]

#566 was detected after seeing the changes affected on the blog.

We have #483 which made it easy to view the static pages but blog posts were excluded...

#563 shows how to iterate through the blog. We so we could generate snapshots of blog posts as well. This would help check for issues in blog posts..

Why check ALL the blog posts

It's true that checking every blog post may seem excessive. Sadly we've had issues that snuck by us due to metadata being incorrect.