Adding a link to the CleanSlate documentation in the Readme.
Add blog templates to the CleanSlate Toolkit.
Improve heading structure for page names.

We were using <h2>’s for page names, where we should use <h1>’s. This
should help with SEO.
Improve indentation and closing tag comments.
What is <r:yield />? Adding a link to the docs explaining this tag.
Add breadcrumbs to the blog templates.