Revert removal of "safe" template tag from blog/news headlines.

Conservancy use HTML entities in their titles.

Remove unnecessary use of "safe" template tag.

This tag marks a variable as not requiring escaping by the template engine,
potentially creating cross-site scripting vulnerabilities, so shouldn't be used
unless absolutely necessary. In these cases, I don't think it's necessary.

blog/news: Add Open Graph metadata to entry pages.

This helps other social media sites generate nice previews for these pages.