Pure Python hashcash implementation

[David Mertz, Ph.D.]

Well, following up on myself.  I sped up my implementation by about
40%, added some more documentation, and added command-line switches
that more-or-less match the C hashcash utility.  The new one is still
alpha level, but it will have a permanent URL at:

  http://www.gnosis.cx/download/gnosis/util/hashcash.py

As the URL insinuates, I'll included this in a future release of
Gnosis Utilities (under the subpackage indicated by the directory). 
But I haven't done that yet (I think I have some other old
user-recommended changes to dig through before doing a new release).

Still, being alpha and all, I would be thrilled to get suggestions or
bug reports.

Yours, David...