Crash when using logfile (-l) argument

[Breakthrough]

From #93, specifying a logfile currently causes the program to exit with a failure:

Downloads % scenedetect -v debug -l BUG_REPORT.txt --input goldeneye.mp4 detect-content split-video
Traceback (most recent call last):
  File "/Users/bman/.pyenv/versions/3.8.2/bin/scenedetect", line 8, in <module>
    sys.exit(main())
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/scenedetect/__main__.py", line 58, in main
    cli.main(obj=cli_ctx)   # Parse CLI arguments with registered callbacks.
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/click/core.py", line 1268, in invoke
    Command.invoke(self, ctx)
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/Users/bman/.pyenv/versions/3.8.2/lib/python3.8/site-packages/scenedetect/cli/__init__.py", line 261, in scenedetect_cli
    logfile = ctx.obj.get_output_file_path(logfile)
AttributeError: 'CliContext' object has no attribute 'get_output_file_path'