Fix licensing resources page

The just-merged PR, #312 (which is terrific, BTW, :+1:) links to a raw Markdown file ([/licensing-resources.md](http://project-open-data.github.io/licensing-resources.md)) by mistake. This PR updates the link to `/licensing-resources`, and ensures that that page renders properly by adding YAML front-matter to the page. 

I also adjusted the formatting of the headers slightly, since the page title is determined by the front-matter -- and the italicized level 4 header below it has been de-italicized and made into a normal paragraph, to match with the header formatting on [/license-examples](http://project-open-data.github.io/license-examples/). I think this is as it was intended.