Fix for headerImage

Did resize when pushing up tabPageHeader.
Even better solution

Same height on userPage and MeTab, based on mobile_retina size.
Results in a crisper banner, as it's downscaled now instead of upscaled.
See https://dev.twitter.com/docs/user-profile-images-and-banners
mobile_retina 640x320 is downscaled to our width 540x270
Merge pull request #119 from Morpog/sailfish-port

Banner image size and resolution fixes