Progress bar

[henryiii]

I've added a progress bar to plumbum.cli.terminal, with auto sizing and iterator support. To use, simply wrap a slow iterator with Progress:

>>> for value in Progress(BigSlowCalcululationIterator):
    pass

Or use a fast iterator with .wrap or use .range:

>>> for value in Progress.range(10):
    # Slow calculations here
    time.sleep(1)

The output looks like this:

[******* 85% *****    ] 0:00:17 completed, 0:00:03 remaining

IPython notebooks are supported, too, through ProgressAuto (which selects text or HTML output based on what is available).

I updated cli.terminal docs.