How to use the phonemizer.backend.SegmentsBackend.supported_languages function in phonemizer

* Add a separator between phones

  $ echo 'hello world' | phonemize -l en-us -b festival -p '-' --strip
  hh-ax-l-ow w-er-l-d

* Phonemize some French text file using espeak

  $ phonemize -l fr-fr -b espeak text.txt -o phones.txt
        '''.format(
            festival='\n'.join(
                '\t{}\t->\t{}'.format(k, v) for k, v in
                sorted(FestivalBackend.supported_languages().items())),
            segments='\n'.join(
                '\t{}\t->\t{}'.format(k, v) for k, v in
                sorted(SegmentsBackend.supported_languages().items())),
            espeak='\n'.join(
                '\t{}\t->\t{}'.format(k, v) for k, v in
                sorted(EspeakBackend.supported_languages().items()))))

    # general arguments
    parser.add_argument(
        '--version', action='store_true',
        help='show version information and exit.')

    group = parser.add_mutually_exclusive_group()
    group.add_argument(
        '-v', '--verbose', action='store_true',
        help='write all log messages to stderr '
        '(displays only warnings by default).')
    group.add_argument(
        '-q', '--quiet', action='store_true',