fix issues with outdated test data, and enable progressbar for demo

reimplement most parts of IO in c sloth

fix bug where witness was initialized to final_hash

Change the python bindings to use actual bytes

Previously ascii hex was used, now we convert at CFFI boundaries

revert converting sloth outputs

tweak buffer sizes to avoid malloc errors

fix bug where data was encoded even if bytes

add progress to verify and general cleanup

cleanup and progress bar