[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
But you're using a very specific example. That concern would be valid if you're expecting a generic `ZincRuntimeException`, but not with this :)