'When --add-header is specific, the value is parsed.'

def test_add_header_parsing(self):

    options = Options()
    options.parseOptions(['--add-header', 'K1:    V1', '--add-header', 'K2:    V2'])
    self.assertEqual(options['extraHeaders'], [('K1', 'V1'), ('K2', 'V2')])
