Use argparse for command line parsing

oslo.config includes the ability to parse command line options [1]. Originally
I thought that Satori should leverage this library for command line parsing.
However, after looking at many of the other command line tools, it is not
really being used. Some more digging turned up
https://review.openstack.org/#/c/57265/ where python-marconiclient replaced
oslo.config.

There appears to be a pretty solid agreement around argparse:
 nova - argparse
 swift - optparse
 glance - argparse
 keystone - argparse
 cinder - argparse
 ceilometer - argparse
 heat - argparse
 trove - argparse
 savanna - argparse
 barbican - argparse

 For this blueprint we should implement argparse and make arguments for
 username, tenantid, password, apikey, region. If not supplied on the command
 line, fall back to the `OS_` environment variables.

[1] https://wiki.openstack.org/wiki/Oslo/Config