Merge pull request #1 from MrSmith33/master

Fix errors while compiling with dub build
Prevent division by zero in Signal2D.divide
Fixed 'Statemen not reachable' warning in Vector.valid
Fixed element-wise assignment warning in loadPNG (readHeader)
Derive source image bit depth instead of hardcoding 8-bit result
Derive source image bit depth instead of hardcoding 8-bit result
Rewrote renderCosPlasma using ColorRGBAf idiom
Replaced tabs with spaces
Added convolution.d
Cast to ushort instead of ubbyte when converting ColorRGBAf into ColorRGBA
Renamed color types
Changed all filters to use new color type names
Added hsv.d
Added chromakey.d
Updated dual numbers implementation
Added hermite.d
Added toMatrix3x3 method to Quaternion
Added basic XML parser
Changed ColorRGBAf to Color4f in dlib.image.hsv
Updated README.md