Command Line Progress Bar - show information about a data transfer.

Bar is a simple tool to copy a stream of data and print a display for the
user on stderr showing (a) the amount of data passed, (b) the throughput
of the data transfer, and (c) the transfer time.

Or, if the total size of the data stream is known: the estimated time
remaining, what percentage of the data transfer has been completed, and
a progress bar. 
