Update for python-guessit 0.7.1

The new python-guessit automatically tries to autodetect the type if "movie" or "episode" are not specified, so the 'autodetect' is not needed anymore.

Without this change, subliminal fails with the following error:

    Traceback (most recent call last):
    File "/usr/bin/subliminal", line 9, in <module>
    load_entry_point('subliminal==0.8.0-dev', 'console_scripts', 'subliminal')()
    File "/usr/lib/python2.7/site-packages/subliminal/cli.py", line 174, in subliminal
    embedded_subtitles=not args.force, age=args.age)
    File "/usr/lib/python2.7/site-packages/subliminal/video.py", line 309, in scan_videos
    videos.append(scan_video(filepath, subtitles, embedded_subtitles))
    File "/usr/lib/python2.7/site-packages/subliminal/video.py", line 203, in scan_video
    video = Video.fromguess(path, guessit.guess_file_info(path, 'autodetect'))
    File "/usr/lib/python2.7/site-packages/subliminal/video.py", line 64, in fromguess
    if guess['type'] == 'episode':
    KeyError: u'type'