Fix dereferencing / free memory issues with GetImageHistogram (gograp…

…hics#147)

Fix crash when destroying *C.PixelWand via GetImageHistogram;
Fix crash when wrongly assuming num colors in GetImageHistogram;

Fix dereferencing / free memory issues with GetImageHistogram (gograp…

…hics#147)

Fix crash when destroying *C.PixelWand via GetImageHistogram;
Fix crash when wrongly assuming num colors in GetImageHistogram;

Add runtime.KeepAlive calls to prevent GC finalizers (refs gographics…

…#120)

Add runtime.KeepAlive calls to prevent GC finalizers (refs gographics…

…#120)

* 126 Added AffineMatrix API

Merge branch '106_ScaleKernelInfo'

ImageMagick 7.x Support

Update README to include info about ImageMagick 7.x support

Imagemagick >= 6.8.9-10