severity level.  This allows the common names to be used for
  severities, not just integers.  This can make configuration data
  less obscure.

- Refactor initialize():
  get_environment_info() pulls information from the environment
  variables, and this gets passed to initialize_log(), which does
  nothing to determine the source of the configuration data.

- New method initialize_with_config():  Load information not provided
  by the environment from a ZConfig section.  This allows the
  environment to override a config file, and avoids having the
  application deal with the specific information needed to configure
  logging.