Sets additional command line options.

def options(self, parser, env):
        """Sets additional command line options."""
        Plugin.options(self, parser, env)
        parser.add_option(
            '--html-file', action='store',
            dest='html_file', metavar="FILE",
            default=env.get('NOSE_HTML_FILE', 'nosetests.html'),
            help="Path to html file to store the report in. "
                 "Default is nosetests.html in the working directory "
                 "[NOSE_HTML_FILE]")