document that k is hardcoded to '\x00\x01\x02...\x0f' at the moment.
document that k is hardcoded to '\x00\x01\x02...\x0f' at the moment.

Signed-off-by: minux <b563c57947dc20eb81988e3e3c22786764c14ca8@gmail.com>

minux/siphash-tiny