We used to use twisted.python.usage.Options, hence we depended upon
Twisted. Now we depend upon "argparse" instead, which is in the py2.7
stdlib (and on pypi for 2.6). This package will still (eventually)
provide Twisted support, but applications which need it will already
express a dependency on twisted themselves, so by removing the
dependency here, we make life easier for applications that don't use it.
