ProgressBar() module to display output to a console or iPython Re: issue#2658

Modified ProgressBar() module to display output to a console or iPython notebook, depending on additional 'interactive' kwarg.

Description of the issue and possible fix here: http://nbviewer.ipython.org/gist/astrocaribe/398d04434430c3f44617

For readability I would suggest:

```
  if value is None:
             value = self._current_value + 1
self._current_value = value
```