Smarter "Read more" links

I've re-worked the link shown on blog "previews." The index page shows the latest 5 posts with truncated previews. This mechanism is much much better now- it shows just the first element of the post, rather than truncating it. If the content is longer than 1 element, it shows the "Read more" link.

For example, this paragraph is not visible from the index page, but it is visible on the blog page. See the commit that makes this change