Description of new feature, or changes

Added the ability to manually render single spinner steps, via:

• 'manual_step' argument when creating Halo class instance
• '.step()' method to trigger single frame to render
• 'test_manual_step' test

Usage

with Halo(spinner='dots', manual_step=True) as spinner:
    for text in ["foo","bar"]*5:
        spinner.text = 'Loading {}'.format(text)
        spinner.step()
        do_something(text)

or

spinner = Halo(spinner="dots", manual_step=True)
spinner.start()
for text in ["foo", "bar"]*5:
    spinner.text=text
    spinner.step()
    do_something(text)
spinner.stop()

Checklist

• Your branch is up-to-date with the base branch
• You've included at least one test if this is a new feature
• All tests are passing

Related Issues and Discussions

Fixes #47 (new feature)

People to notify

@steelman