Fix <em> tag styling

People have apparently been misusing the <em> tag in OwnCloud (https://twitter.com/jancborchardt/status/504004742138572801). Rather than fix the occurrences, OwnCloud made the <em> tag semi-transparent. This means that emphasised text in news feeds is actually de-emphasised. This rule applies only to the news app content and puts the <em> tag back to its normal full-opacity, italic style.