Synchronous spinner

Support synchronous spinners which switch frames upon explicit request from a working thread like.

with Halo(spinner='dots') as spinner:
  for f in files_to_load():
    spinner.next(text="Loading %s" %f) # or .step(), or .tick(), or…
    do_load_file(f)

This can (as far as I understand) be achieved with .frame() but isn’t as concise as the above. Possibly don’t render new frame more often than interval.

[JungWinter]

How about this way? I think it can do what you want.

with Halo(spinner='dots') as spinner:
   for f in files_to_load():
        spinner.text = 'Loading {}'.format(f)
        do_load_file(f)

[foster999]

Happy to update #132 and check it still works, if the feature might still be of interest @manrajgrover?