Use LAB instead of YUV

There’s a bug somewhere, the colors are wrong.
Reference for D65 values
Fix a typo
Fix another typo
Color difference using CIE 2000 algorithm
Proper RGB -> sRGB conversion on Mac

iOS doesn’t need conversion because the native device color space is
sRGB
Update README
Correctly scale XYZ values
Update README
Remove redundant comment

Already explained in ColorSpaceConversion
Fix headers once and for all
Merge pull request #7 from indragiek/lab-space

Use Lab color space and CIE 2000 instead of YUV