- disabled opengl (performance issues in Qt 4.7)
 - numerous caching changes (disabled deviceCoordinateCache due to performance issues)
 - speed up loading large images in ImageView
 - bugfixes from Ingo Breßler
 - Transform rotation bugfix
 - Added debug module
 - Major performance enhancements for scatterplot, fixed point clicking issues
     ** API change for scatterplot click signals
 - Drawing on ImageItem is working well now
 - PlotItem downsampling no longer uses scipy.signal.resample (this was creating artifacts)
 - Fixed ViewBox behavior when aspect-locked