Rotating buffer

[RCasatta]

This library cannot consume Read by design because it needs a borrowed slice to create objects.
A rotating buffer filling data from a Read input and producing borrowed objects could overcome this limitation and read from streams. The buffer should rotate back every once in a while to be limited in size. It must be long enough to support the maximum size of the object to be read, luckily bitcoin objects are limited in size by consensus so there is an upper limit, at worse 4MB.