include hexdump in reproducible comparison

compare jars using BSD's hexdump since it works on GNU and OSX
get detailed zip comparison from `zipinfo -lv`
Remove CacheWordActivityHandler information

Remove all information related to CacheWordActivityHandler from
README.md to prevent new user wasting time looking for it. It was
removed since over a month ago, based on
https://dev.guardianproject.info/news/193.