Constructor. big - Number of updates before completing a progress
output line. small - Number of updates before outputting a progress dot.
name - Name of the items being processed. stream - Stream to send
progress output to. Defaults to sys.stderr.
Update(self,
step=1)
Update the progress counter by an increment of size step (default=1).
Well output progress dots or line information to the stream if reached an
appropriate big or small increment.