Release Notes update

I have just pushed a couple of small changes in Release Notes. The first, BZ#588953, adds a new section, a couple of paragraphs. Users of varnish are required to make manual changes to their configuration file. The second, BZ#590492, is especially annoying. There was a stray period inside a couple of links which broke the link. Although there is no new language at all, I think it may poison as many as three strings (or as few as none). Thanks --McD