Demosaicing Bits in example from README.md

[schmauder]

in the example of the README.md file i had to change line

let pixlow = (pix&0x0f) as u8;

into

let pixlow = (pix&0xff) as u8;

else i got dramatic posterization. i don't know whether this is a typo or has to do with the bit depth of my camera (14-Bit, arw format, Sony IlCE-7SM2).