pyminer: Fix memory leak, refactor to be more pythonic, maintainable, and possibly faster
pyminer: Fix memory leak, refactor to be more pythonic, maintainable, and possibly faster

Pull #4483.

Note that pyminer is not currently functional due to the removal of
getwork in cf0c47b.

wastholm/bitcoin,wastholm/bitcoin,wastholm/bitcoin,wastholm/bitcoin,wastholm/bitcoin,wastholm/bitcoin