fix changelog to link to hkdfexpand
fix changelog to link to hkdfexpand

dstufft/cryptography,dstufft/cryptography,sholsapp/cryptography,bwhmather/cryptography,dstufft/cryptography,kimvais/cryptography,Ayrx/cryptography,Ayrx/cryptography,dstufft/cryptography,Ayrx/cryptography,kimvais/cryptography,sholsapp/cryptography,kimvais/cryptography,Hasimir/cryptography,bwhmather/cryptography,dstufft/cryptography,Hasimir/cryptography,sholsapp/cryptography,Hasimir/cryptography,skeuomorf/cryptography,bwhmather/cryptography,Hasimir/cryptography,skeuomorf/cryptography,Ayrx/cryptography,skeuomorf/cryptography,sholsapp/cryptography,kimvais/cryptography,skeuomorf/cryptography,bwhmather/cryptography