* Construct unpacking functions for byte format up front to save time
wasted on parsing format string every iteration.
* Store length ahead of time as the overhead adds up.
* Reduce object attribute lookups in hash functions.
* Clean up lib pkg API changes. Unit test new "public" API members.
Underscore prefix for internal hash module funcs. Make bytes.fromhex a
public function.
* Document recent performance findings.
0c2e5c6368