add a "--verbose" option that writes to stderr if it finds anything to omit

Also cleaned up some flakes noticed by pyflakes, and make the scrub() be @classmethod instead of @staticmethod so I could use the class for the verbose output.

caveats:

* there are no unit tests of this patch
* now your logs of your stderr have potentially sensitive information in them
* the implementation of arg parsing is very low-tech; (a *good* way to do arg parsing is the "argparse" module)
fix up verbose printouts, don't print out large data
add -v -v mode which prints out the details (potentially sensitive, potentially bulky)

remove spie, which appears to do nothing
Merge pull request #21 from zooko/verbose-option

Verbosity argument.