Made notification box a rounded rectangle.
Message is not centred in in box, and continues outside the box instead of wrapping
Added Test cases for PDXMessageView, using Facebook's Snapshot test harness
Removed constraints on messageView and replaced them with calculations for locating the view
Made existing errorMessage label into a rounded rect.
Changed some constraints
Fixed sizing (and placement) of twitterHandle if user changes their preferred size of  text
Notifications fixed