Use a fixed lenght buffer in writePseudoRandomBytes()

This will reduce memory usage.

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Helped-by: Juan Batiz-Benet <juan@benet.ai>
Merge pull request #4 from chriscool/seed

Use a fixed lenght buffer in writePseudoRandomBytes()