Added missing HashContext documentation
Added missing HashContext documentation

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