Removed the recommendations for progressive JPEG encoding (from the UI) based on the Radware study showing that people are happier with top-down baseline by quite a large margin: http://www.radware.com/neurostrata-fall2014/?utm_source=slidernav&utm_medium=slider&utm_campaign=neurostrata-fall2014

Not recommending against progressive images at this point, just leaving it neutral but this is the only end-user data we have to date and it's pretty compelling.
Merge branch 'master' of github.com:WPO-Foundation/webpagetest