[FINAL] Validating hash when downloading/extracting bundles.

An attempt to validate bundle hashes as they come in the door.  I was able to sha1 hash the file contents as they stream in, avoiding secondary passes over the file contents.

This is a follow on attempt to #32
This could be a false positive. Maybe the hash validation throws some other exception, but not due to an invalid hash. You're asserting it's the generic `ZincException` so you don't really know :)